The summer arrival from Atletico Madrid has battled with injury this season.
Mendieta told Goal: "When analysing football today, not many players play every match. There is competition within the team and especially in big clubs like Atlético Madrid, but it also depends on the number of matches played.
"Sometimes some do not see it and I can understand why he feels he should play more, and I think it will be a similar situation for him at Arsenal. In whatever team he plays, the situation will be similar, there are not many players who play every week.
"He must understand that football is played in this way nowadays. Hopefully, his development will not be stopped by any injuries, and this is a new environment for him."