10 U21 players poised for a breakthrough season in 2026/27
Ten under-21 players who could make 2026/27 their breakthrough season, with early-season stats, rising valuations and the stories behind their new opportunities.
A spectacular goal can introduce a young player to the world. A place in the starting XI every weekend tells us something more useful: his manager is beginning to depend on him.
Across Europe, the opening weeks of 2026/27 have delivered both. Paris Brunner is scoring regularly for Monaco. Flávio Gonçalves has gone from fleeting appearances to meaningful responsibility at Sporting. Elsewhere, a change of club is giving familiar prospects the opportunity to become much more than promising names.
Players such as Lamine Yamal, Pau Cubarsí, Warren Zaïre-Emery and Estêvão are intentionally absent: each has already made a significant senior breakthrough. Those names are examples, not an exhaustive list of the established under-21 players left out. This article focuses on players whose growing roles suggest that 2026/27 could be their breakthrough season.
That might mean becoming a regular starter, emerging as a match-winner or proving themselves in a new league. Each player’s case is slightly different—and those differences matter.
To explore the broader age group through valuations, read our 10 most valuable U21 players in 2026. That ranking uses age 21 or younger; the breakthrough selection here is strictly under 21 at the stated cutoff.
Several are also rising sharply in Oddsivio’s estimated player values. Those movements add another angle to the story, with the dates made explicit below. These are model estimates, not agreed transfer prices. They can change with performances, playing time, club context and season projections; a percentage increase does not isolate how much a player has improved.
Our guide to how Oddsivio estimates player values explains the inputs, confidence levels and limits behind these numbers.
Researched on 23 September 2026. Match statistics run through 20 September; all players were under 21 at that cutoff. Figures are domestic league totals unless another competition is specified. Values use the latest weekly snapshot, 21 September. Percentage changes use unrounded estimates, while euro figures are rounded for readability.
1. Paris Brunner, Monaco — an opportunity seized
Age: 20 | Forward | Ligue 1: five starts, 390 minutes, four goals
Last season, Brunner made one Ligue 1 start and finished without a league goal. This season, he has started all five of Monaco’s opening league matches and scored four times.
That is a substantial change in both opportunity and output.
His two goals against Marseille offered a particularly appealing introduction. The first came from meeting Aleksandr Golovin’s delivery with his head; the second followed a solo run through the defence. Different situations, different solutions, the same scorer. Monaco’s match report describes a forward capable of contributing more than one type of finish.
The goals have continued beyond that standout evening. Brunner scored against Strasbourg and Lens, while two Conference League qualifying goals brought his competitive total to six. Following the Lens win, Filipe Luís highlighted his growing confidence, energy and involvement. Monaco’s September assessment
His Oddsivio estimated value has climbed from €12.7m on 3 August to €23.0m on 21 September, an 81% increase. That is a sizeable reassessment over the opening weeks, although an early-season estimate for a developing player can still move quickly in either direction.
Four league goals do not establish a season-long scoring rate. Five consecutive starts, however, give Brunner something every young striker needs: another opportunity to score when the previous chance has gone begging.
2. Franco Mastantuono, Fiorentina — room to become the main attraction
Age: 19 | Attacking midfielder/winger | Serie A: five starts, 377 minutes, three goals
Mastantuono arrived in Florence with a famous parent club and a straightforward task: turn an enormous reputation into regular influence.
Real Madrid confirmed his season-long loan in August. Fiorentina have immediately given him a sustained run, starting him in each of their first five Serie A matches.
Then came Venezia.
His hat-trick included two strikes from outside the penalty area. According to Lega Serie A, it made him the youngest foreign player to score a hat-trick in the competition’s history. That is quite an introduction to Italian football.
There is an important detail behind the headline: all three of his league goals came in that match. His next challenge is spreading that influence across ordinary weekends.
The supporting numbers offer encouragement. Ten key passes—passes leading to shots—and nine successful dribbles suggest ways to affect games even when the long-range attempts stay out. Fiorentina have given him the stage. Sustained performances will determine how completely he makes it his own. Mastantuono’s Oddsivio profile
3. Gianluca Prestianni, Benfica — from contributor to match-winner
Age: 20 | Winger | Primeira Liga: seven starts, five goals, three assists
Prestianni already had a meaningful place in Benfica’s squad. The breakthrough possibility here is about the size of his contribution.
Last season, he produced three league goals and five assists across 29 appearances. Seven games into this campaign, he has already matched those eight combined goal contributions, with the balance shifting towards scoring himself.
His goal against Marítimo captured the appeal. Benfica’s account of the move describes him winning possession in his own half, carrying the ball forward under pressure and finishing into the far corner. He helped create the opportunity, transported it upfield and completed it.
That sequence sits alongside 22 successful dribbles and 17 key passes in the league. There is substance behind the finishing.
The change is visible in his Oddsivio value history, too: €14.1m on 3 August became €26.6m on 21 September, up 88%. His new goals-and-assists total is the tangible football story; the valuation gives us another way to track his changing profile.
The question now is whether he can sustain that variety when opponents give him more attention. Scoring, creating and beating defenders provide several routes into a match. Keeping all three available could make this the season Benfica begin expecting decisive moments from him.
4. Charalampos “Babis” Kostoulas, Brighton — the starts are catching up with the talent
Age: 19 | Striker | Premier League: four starts, two goals, one assist
The clearest number in Kostoulas’s case is four.
That is how many Premier League starts he has already made this season—twice his total from the whole of 2025/26.
His performance in Brighton’s 3–0 victory over Arsenal gave that increased responsibility a memorable demonstration. He forced an early save from David Raya, contributed to the move for Pascal Gross’s opener and then struck Brighton’s second from the edge of the penalty area before half-time. Brighton’s match report
There was more to the afternoon than the finish. Kostoulas was involved while Brighton were building their advantage, giving the performance a broader significance than a young substitute arriving to decorate an already comfortable scoreline.
His Oddsivio estimate has more than doubled, moving from €18.0m on 3 August to €37.4m on 21 September, a 108% increase. That movement covers the whole period: it would be misleading to describe the Arsenal goal alone as adding €19m to his value.
Two goals and an assist are an encouraging start. The larger opportunity is becoming a forward Brighton can rely on throughout a match.
Watch how often he remains involved when chances are scarce: offering a passing option, linking attacks and helping the team apply pressure. Those contributions can keep a young striker on the pitch long enough for the goals to follow.
5. Gessime Yassine, Strasbourg — giving defenders a problem to solve
Age: 20 | Winger | Ligue 1: five starts, two goals, one assist, 18 successful dribbles
Yassine’s first Ligue 1 goals arrived together: a double that helped Strasbourg beat Lens 2–1.
Ligue 1’s profile of that performance traced his progress from Dunkerque to a growing role in Strasbourg’s attack. His first season in the top flight brought 12 appearances. This campaign has begun with five consecutive starts.
The statistic that makes him especially interesting is 18 successful dribbles.
Beating an opponent with the ball can force another defender to leave his position, opening space for a teammate. That makes Yassine worth watching even during stretches when his own name stays off the scoresheet.
Over the four weeks from 24 August to 21 September, his Oddsivio estimated value rose from €8.3m to €13.0m, an increase of 57%. That shorter comparison uses estimates made with the same Strasbourg club context throughout.
The next step is making those advantages count more often. Both league goals came against Lens, so the scoring has yet to become a regular feature.
Still, 434 minutes from five matches suggest he is getting the playing time to develop that final decision: when to carry on, when to release the pass and when the shot is there.
6. Flávio Gonçalves, Sporting CP — 23 minutes to a proper role
Age: 19 | Winger | Primeira Liga: six starts, 414 minutes, three goals, one assist
Last season’s league contribution amounted to three substitute appearances and 23 minutes.
This season, Gonçalves has already made six starts and contributed directly to four goals. Few players on this list have experienced such a clear change in their everyday importance.
Recognition has followed. He won Liga Portugal’s Young Player of the Month award, ahead of Prestianni and Arouca’s Taichi Fukui, and received his first Portugal under-21 call-up in September.
Those milestones support what the minutes already show: he is progressing beyond occasional introductions to senior football.
Three goals are an excellent return, although eight recorded league shots are far too few to establish how prolific he will become. His season will also be shaped by the less eye-catching work that helps him retain his place when a finish goes wide.
For now, Sporting are providing the opportunity, and Gonçalves is giving them reasons to keep providing it. Gonçalves’s Oddsivio profile
7. Vasilije Adžić, Sassuolo — making his minutes impossible to ignore
Age: 20 | Midfielder | Serie A: five appearances, three starts, three goals, one assist
A loan move is supposed to help a young player’s development. Adžić has already used his to give his parent club an uncomfortable evening.
After joining Sassuolo on loan from Juventus, he scored the winner against Juve in September. Afterwards, he spoke about the confidence Alberto Aquilani had given him and the importance he felt within the group. Sassuolo’s post-match interview
That goal sits within a run of scoring in three consecutive league appearances, against Bologna, Juventus and Monza.
His contribution has been striking for the time available: three goals, one assist and 12 key passes in 222 minutes. It is also a small sample, with his last two goals coming from substitute appearances.
The next stage is earning longer stretches in the side and sustaining that influence. Adžić has made a persuasive early argument for more minutes. What he does with them could turn a productive loan into a defining season. Adžić’s Oddsivio profile
8. Adam Daghim, Hoffenheim — contributing every weekend
Age: 20 | Forward | Bundesliga: four starts, two goals, two assists
Daghim’s opening sequence is unusually tidy: a goal against Köln, an assist against Dortmund, another against Stuttgart and a goal against Paderborn.
Four league matches, a direct goal contribution in each.
Hoffenheim signed him permanently from Salzburg after his loan season at Wolfsburg. At the time, sporting director Andreas Schicker highlighted his speed, development potential and existing Bundesliga experience. The Bundesliga’s transfer announcement
He has already matched the two league goals he scored across 27 regular-season appearances for Wolfsburg. The Bundesliga’s current statistics also confirm his two assists.
His Oddsivio estimated value increased from €10.5m on 31 August to €13.4m on 21 September, up 28%. This comparison begins with his first non-provisional Hoffenheim snapshot, rather than using a temporary estimate during the change of club context.
Hoffenheim have lost three of those four matches, which gives his start a different context from a young attacker thriving in a dominant team. He is finding ways to contribute while the collective results remain difficult.
Maintaining that involvement through a longer, uneven run would strengthen his case considerably. Daghim turns 21 on 28 September, just after this article’s age cutoff.
9. Luka Vušković, Brighton — the Premier League breakthrough candidate
Age: 19 | Centre-back | Premier League: five starts, 438 minutes, one goal
Vušković needs a precise introduction: this is a potential Premier League breakthrough, following an already impressive season in Germany.
He played 28 Bundesliga matches for Hamburg last season and scored six goals. His senior ability had therefore been demonstrated before Tottenham agreed his transfer to Brighton in July.
The new question was how quickly he could establish himself in England.
Five starts from Brighton’s first five league matches provide an encouraging answer. He also scored against Leeds, as recorded in Opta’s season profile.
His Oddsivio estimated value has risen from €36.3m on 24 August to €56.5m on 21 September, up 56%. Both endpoints use Brighton club context. Starting the comparison earlier would mix his progress in England with the model’s transition from his Hamburg season.
For a centre-back, though, the more revealing moments often pass without a celebration. Against Arsenal, he intercepted to stop Christos Tzolis when the attacker threatened through the middle. Brighton’s report picked out that intervention before the hosts took control.
His progress should be judged through that work: recognising danger, handling different opponents and making sound decisions repeatedly. A near-continuous place in Brighton’s defence gives him an excellent platform to show it.
10. Luca Weinhandl, Sturm Graz — the youngest player on the list
Age: 17 | Midfielder | Champions League qualifying: four starts, 289 minutes, one goal
Weinhandl is the discovery pick: a teenager already receiving meaningful European responsibility.
Sturm’s club profile describes a player who progressed through their youth teams, gained second-division experience and made his senior debut in 2026. He was also part of Austria’s run to the 2025 Under-17 World Cup final.
This season has brought another step. He started four Champions League qualifiers, with UEFA recording 289 minutes and one goal. That goal came against Hearts after combining with fellow youngster Jacob Hödl in Sturm’s 4–0 home win. Sturm’s match report
He subsequently played the full Europa League opener against Rennes, which finished 0–0. Sturm’s report from that match
At 17, repeatedly being trusted to start European matches is a significant part of the story. His next challenge is sustaining that responsibility as the season becomes more demanding.
Sturm’s European campaign gives us a useful place to follow it—and gives Weinhandl the chance to make his name familiar well beyond Austria. Weinhandl’s Oddsivio profile
Statistics and player-value estimates come from Oddsivio’s covered competitions; the linked club, league and UEFA reports provide additional context. Ratings are provider ratings on a 0–10 scale. Value charts use non-provisional snapshots within the same club context, so comparison start dates vary. Gonçalves has only two weekly estimates; Weinhandl has no estimate yet. Small early-season samples describe the start, not a prediction of how the season will finish.
For the wider early-season picture across every age group, explore our eight standout players of 2026/27 so far.