I think maybe there are a lot of ways this exercise could be answered. Am I right or wrong?
Shouldn't it be "aux tous les matchs avec son équipe"? We just had an exercise with "...participaient aux courses...". Since "matchs " is plural then I would think "aux" is appropriate.
That would be "He competed in the all the games …". Don't forget that "aux = à + les".
In French, It's more common to say : "... à tous les matchs de son équipe." Why isn't that translation accepted?
That would translate as 'in all his team's matches/games."
The different emphasis may or may not be important depending on the context.