Why can 23-year-olds play at Euro U21s?

Players aged up to 23 years old can feature at the European Under-21 Championship, under way in Slovakia.

That is because its player registration rules are designed to ensure players can feature through an entire tournament cycle - from the start of the qualifiers through to the finals.

It means that, for the 2025 tournament, players can feature if they were born on or after 1 January 2002 - meaning they were 21 or younger at the start of the year in which qualification began.

The tournament, which started on Wednesday, consists of 16 nations, each with 23-strong squads - a total of 368 players.

Of those, 205 were aged either 22 or 23 on the opening day of the tournament - 55.7% of the total number of players. A total of 73 players were aged 23 on the tournament's opening day - 19.8%.

Defending champions England, managed by Lee Carsley, are the only nation without a 23-year-old currently at the tournament. Middlesbrough midfielder Hayden Hackney does turn 23 two days before the final on 28 June.

England's players in the squad who are aged above 21 include captain James McAtee of Manchester City, Liverpool's Harvey Elliott and Newcastle defender Tino Livramento, who is the only member of Carsley's squad to have been capped at senior level.

All 16 nations have a minimum of nine players who are 22 or 23 years of age. Georgia's squad has 19 players who were aged 22 or 23 on the tournament's opening day.

The oldest player at the tournament is Stoke City's Million Manhoef, who is in the Netherlands squad. He was born on 3 January 2002.

The rule regarding the cut-off date - meaning players can be no older than 23 years and six months - is a long-standing one.

But when it was first staged as an Under-21 tournament in 1978 - having previously been an Under-23s competition - each country was allowed two players over 21.

Yugoslavia won the 1978 tournament spearheaded by 26-year-old striker Vahid Halilhodzic, who scored four times in the two-legged final against East Germany - including a second-leg hat-trick, external - and was named Player of the Tournament.

Of England's 26-man senior squad named by Thomas Tuchel's for this month's matches against Andorra and Senegal, seven would have been eligible to play in the Under-21 tournament.

That includes Real Madrid midfielder Jude Bellingham, who has 43 senior caps but does not turn 22 until a day after the Euro Under-21 final.

Burnley goalkeeper James Trafford and Chelsea trio Cole Palmer, Levi Colwill and Noni Madueke were all part of England's 2023 Euro Under-21-winning squad and would have been eligible for selection this time around.

Arsenal teenager Myles Lewis-Skelly, 18, was the youngest member of the senior Three Lions squad against Andorra and Senegal. Had he been named in the Under-21 squad, he would have been England's second-youngest player, after Gunners colleague Ethan Nwaneri.

Other players who could have been picked for the Under-21s include Everton centre-back Jarrad Branthwaite and Southampton's Taylor Harwood-Bellis.

In some cases, players have missed the Euro Under-21s as they are away with their clubs for the 2025 Club World Cup in the United States, starting on Saturday (local time).

New Chelsea striker Liam Delap was in line to feature at the Euros, but having completed his moved from Ipswich Town the night before Carsley named his 23-man squad, he was left out and is instead at the Club World Cup.

Midfielder Jobe Bellingham was named in the initial squad, but was replaced less than 24 hours prior to England's opening victory over the Czech Republic on Thursday after completing a move to Borussia Dortmund. Bellingham was replaced by West Bromwich Albion's Tom Fellows.

Manchester City have a number of players eligible for the Euros who are instead going to the Club World Cup, including new signings Rayan Cherki and the 20-year-old duo of Rico Lewis and Nico O'Reilly.

City's Spanish midfielder Nico Gonzalez would have been the joint-oldest player at the Euros, had he gone there instead of the Club World Cup.

Spain striker Samu Aghehowa, who plays his club football for Porto, was his country's top scorer in Euro Under-21 qualifying - but he has also gone to the Club World Cup.

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