Rooney was suspended for Saturday's defeat to Newcastle United.
"I think we've got a really good record when Robin and Wayne play together," said Moyes.
"But we knew at the start of the season that there would be times when players would be injured or suspended. Wayne's played great and we do miss him undoubtedly because he's a great player.
"I think we can play better but there were a lot of games last year where Manchester United didn't play particularly well and maybe in a game like that sneaked it with a goal."
For breaking stories and all the great banter like us on Facebook: facebook.com/tribalfootball