I think exactly the opposite. Ranieri has so far put faith in him by playing him often, almost always when possible, so there's no pressure on him, no reason for him not to have confidence, yet he still fails to deliver.
Not all players are impact players, not everyone can come off the bench and have a great game. And most of the players will tell you it's harder to come from the bench than play from the beginning.
I like Hamsik a lot, but he played LM for the national team and he sucked there. He was completely out of position. As soon as the coach moved him to the center (in the same match) he was a completely different player.
George Best regularly trained drunk or hung over, yet he was able to score three goals in the evening.
In other words, what is the purpose of training well if you can't do anything in the match and vice-versa?