
The 2025-26 Champions League will get underway on Tuesday and one of the two early kick-offs takes Mikel Arteta back to the Basque Country.
Arsenal play in the 5.45pm (UK) slot against Athletic Bilbao while PSV welcome Union St Gilloise in a simultaneous curtain-raiser for Europe's premier club competition.
The Gunners will go on to face Bayern Munich, Inter Milan, Atletico Madrid, Club Brugge, Olympiakos, Slavia Prague and Kairat Almaty in their other Champions League fixtures and, like the other participants in the competition, will be affected by two significant rule changes.
Last season was the start of a new era of the Champions League, with the old group phase replaced by a single 36-team mono-table under the so-called Swiss model.
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The structure was deemed a success not only in the Champions League but in the Europa League and Conference League too.

Arsenal fell foul of a quirk in the rules, though, and UEFA has moved to correct it for the new season.
After finishing third in the league phase, Arsenal moved automatically into the next round while Real Madrid required a play-off. When the two met in the quarter-final, Arsenal had to play the second leg at the Bernabeu rather than the preferred home game.
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UEFA has accepted that the automatic league phase qualifiers shouldn't be disadvantaged in such a way and acted accordingly.
"Seeded teams, i.e. teams ranked 1 to 4 after the league phase, play the return leg at home in the quarter-finals, and teams ranked 1 and 2 also play the return leg of the semi-finals at home. If a seeded team is beaten in any round, the team that eliminates them takes over their seeding position in the bracket path (i.e. the higher ranking for seeding purposes is not recalculated after each round)," explains the governing body in its updated Regulations of the Champions League document.

In other words, finishing higher in the league phase maintains an advantage right into the latter stages of the knock-out phase.
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In a second update to the regulations, UEFA has addressed the matter of its competition squad restrictions, which have left the likes of Federico Chiesa of Liverpool, Tottenham Hotspur striker Mathys Tel and new Chelsea signing Facundo Buononotte looking in from the outside.
UEFA has updated its Champions League squad rules
However, the clubs taking part have greater flexibility than it first appeared.
Champions League squads can now include an additional temporary replacement in case of long-term injury or illness to a player named in their lists within the first six games.
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Explaining the change in a statement, UEFA said: "The Executive Committee approved an amendment to the 2025/26 UEFA men’s club competitions’ regulations to admit the temporary replacement of a maximum of one outfield player with long-term injury or illness during the league phase until matchday 6 included."
Topics: Football, Champions League, Arsenal, Athletic Bilbao