I'm not disagreeing with you about him making mistakes, but if this season has taught us anything is that Martinez isn't gonna be benching a 19 year old centre back who's playing in one of the most form teams in Europe atm and keeps looking better.
Martinez isn't afraid of players (especially younger ones) making errors, as he knows that the experienced players will more than likely make up for it (e.g. Howard yesterday). Yes it was a heart in the mouth moment, but Howard got there, got it to Baines and Cazorla had being drawn in and was way out of position. 30 seconds later we were 1 up.
When Jags does return i'm sure he'll be back in the team, but there's no need to rush him back if it's gonna cause more harm than good!