I totally agree and it's Pellegrini's greatest failure during his 3 years here.
He replaced Nasri in the CL squad with Kelechi and then in a game where Kiev, a side who have never beaten an English side away from home in the CL needed to score 3 goals, he doesn't even put him on the bench! If that wasn't a game for a couple of younger players including him to be played I don't know what is. He is shit scared of trying anything new and just sticks with the tried and tested players, a few of who, who have basically let him down all season.