The signing has given everybody a real boost at Old Trafford but the manager admits he'll have plenty of headaches trying to pick his team.
"It's not going to be easy," he stated. "I've brought a complication to my life now really.
"I think absolutely it had to be in my estimation for bringing Robin here [to combine him with Wayne Rooney]. We had to say: 'What would be the combination?'. Robin can actually play in two or three positions as he has done at Arsenal. But last season proved what his best position was - No1, furthest up the pitch. 37 goals and 30 league goals - that itself tells you what his best position is.
"My situation now is I have the possibility that I can play Rooney through, van Persie through, Chicharito through and I've got Danny Welbeck, who can play through. I've also got Shinji Kagawa playing in that hole behind and he's a fantastic, young footballer. That's my dilemma and was also have young Federico Macheda, who is only 20 years old and still improving."