The Japan midfielder hit a hat-trick in the 4-0 rout.
"Shinji was fantastic," said Rooney.
"He keeps putting himself in positions where he can get a shot at goal or play someone in.
"He is great with his runs too. If you can pick him out he is cruel with his finishes.
"Goals-wise it was his best performance but he has played other games well as well without scoring."
Does Kagawa's hat-trick guarantee him a Real Madrid start? Has he proved himself a United player? Give us your shout below...