Rooney played 65 minutes in England's international friendly against Scotland but hamstring and shoulder injuries have restricted his pre-season involvement.
The 27 year old was not deemed fit enough to play for United in the Community Shield against Wigan Athletic. His lack of involvement has been linked to the wrangle over his long-term future at Old Trafford.
Chelsea have had two bids rejected by United with the club's hierarchy reportedly informing the Blues that Rooney is not for sale at any price this summer.
"As I've said before he's not for sale," Moyes told Sky Sports News.
"I think I'll need to see what he's like when I get back. When I get back I'll assess him and see how he's done.
"I watched the game last night and I thought for the 65 minutes or so that he played he done well. He ran around, got himself some fitness but it was his first outing in any real competitive game."
While attempting to head off interest in Rooney, Moyes has been unable to add to his squad after having two bids for Cesc Fabregas rejected by Barcelona.
But the Scot is confident United will make new additions before the end of the window, while reaffirming his belief in the current squad.
"I'm confident we'll have players in before the start of the season," Moyes said. "We're involved in several players we're looking at and that will continue.
"Will we get them before the deadline I hope so but we're working very hard to do so. It was always going to be a difficult window for me personally because I only joined Manchester United on the 1 July.
"To get to know the players and to get to know the market and yes of course I was working on it in the summer trying to see but it's not the same until you've worked with the players and been around them.
"What I do know is the group of players we've got are a great group of players. They won the Premier League last year.
"We've got a lot of young, exciting players a lot of them played for England last night so it's important that we focus on a lot of the players that we've got at Manchester United and how well they've done last year and there's not much change so hopefully they'll be able to continue from last season."
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