But Macari admits Rooney will have to work hard to win back his place in the team from Mexican striker Javier Hernandez.
Macari: “Wayne is going to have to work to get back into the team because the manager is not going to throw him straight in on reputation alone.
“Wayne has got to get back to full fitness, show his sharpness and hunger and wait for his opportunity, especially as it looks as though he is going to be out for four or five weeks because of his injury.
“But there’s no doubt he will be vital to United’s chances of competing for the Premier League and the Champions League.
“Wayne’s strength is scoring goals, as he demonstrated last season. If he can get back to a fraction of the form he could make all the difference.”