So you have to take what he says with a grain of salt. It's fine. 99% of people are conditioned to not really say what's on their mind.
But on the field, you just have to look at his play to see he's not complaining. He's probably the toughest player in the league. He's a grinder. No one would work that hard on the field to be successful if he had major issues with the coaching, offense, etc.