The only reason it is mental is that LA has gameplanned him out. They have forced him to shoot the ball, or be a completely useless body out there on offense. This has clearly gotten into his head.
Rondo is going to be fine in the longrun...but I am not confident he is going to be able to do much for the rest of the series.
The one thing he should be doing though, is taking advantage of being ignored, and absolutely attack the boards. He should be running everywhere trying to find seams, and basically causing havoc.