And the England skipper can't wait to get the season started.
"It's always great to get a new manager but when you get someone in the stature of Jose Mourinho he's great to work under and he's brought a winning mentality back to the club," Rooney told Manchester radio station Key 103.
"Manchester United as a football club we have to win and we have to deliver for him.
"There's pressure on the players but we're ready and I think this season we'll give a real challenge on all fronts.
"He's come in, he's been great with the players. The training has been hard but enjoyable.
"We're ready, we're working hard. We know it's a big season for us.
"He's made, in my opinion, some great signings who have gelled in really well with the squad so it's exciting times."
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