I don't think he's been disinterested. I just don't think he has the legs to play in the center any more. He is a big lad and it takes a lot to get that frame moving over a short distance. Once in motion he is still a force but not as able to make the subtle adjustments to get past people as he used to. His game has to change to utilize what he is still great at, excellent first touch, fantastic vision, inch perfect passing and a monster to move off the ball. So IMO he can't play a CM, DM, CB or FB. That leaves an attacking role, like Nasri or Silva or as an actual striker.
Again I honestly don't believe the man is lazy or uncommitted, just not being played in a role that suits his humongous aging body. (He said speaking as a humongous aging body himself ;-) )