I could be wrong here, but I think it's more down to skill level/formation & tactics rather than age.

All age will do is tire the player quicker than a younger player, but even that is not consistent as my team of mixed ages seem to tire at the same rate (all drop 20% in the first half).

I'd suggest looking at your formation setup for each game and make sure it counters what ever your opponent has set and then check during the match and counter any changes.

Just my thoughts. ☺