A player gains routine from playing matches (except friendlies). Routine makes a player perform better and more consistently. 

National cup and league matches are worth 0.1 pts of routine per match. Champions League games gives 0.2 pts.

Don't underestimate the effect of routine! If your team is too inexperienced, try mixing in some older players with routine, they will help your younger players in the match. Routine gives up to 12 extra skill points in all skills when a player has around 50 in routine.

The first routine points will give a higher boost than when a player has very high routine. 

Routine made simple: 
Routine 10 = +4 to all skills of the player 
Routine 25 = +8 to all skills of the player 
Routine 50 = +12 to all skills of the player 
Routine 100 = +14 to all skills of the player 

NB! A player needs to play at least 1 minute or more anytime during a match to get routine.