Lampard is miffed at being given a truncated role - he hasn't ever blamed the manager for it (afaik). It's obvious he would be a little concerned about this, but that concern can also be due to being worried about his form. From what I remember, he said once (I'm paraphrasing here) - that he doesn't know why he's in and out of the side and hasn't asked for an explanation. Which means he respects the decision, so much for any animosity. AVB also said something about not needing to give explanations, though I really don't know if that was in response to a journo asking him about Lampard. Doesn't look like trouble to me, more like a manager doing what he's meant to do (take decisions) and the player respecting it while at the same time wanting to be involved more, a perfectly natural thing.