I disagree that we don't need to buy if Rooney is sold. It's not about lacking cover. We have enough players for the attacking midfield/support forward role. It's about a lack of end product. I have complained a lot about Rooney's poor performances last season, but he put up some decent numbers. He should have been a lot better, but you can't complain about his actual end product. We take those away and we're missing a lot of goals and assists.
Kagawa has not yet shown that he can replace those goals and assists. Our wingers barely scored last season. Nani coming in and playing often would give us a lot more end product than Valencia and Welbeck were able to produce all of last season. No idea if that will happen, though. If Rooney leaves, we need our wingers and attacking midfield players to step up substantially or we need to buy a replacement.
I just can't see any reason to sell him to Chelsea. Even if he kicks up a fuss about it. He is a damn good #9 and him going there will help them a lot. Mata, Hazard and Oscar creating for him is a pretty scary thought.