Rooney missed Wednesday night's 1-1 Champions League draw with Shakhtar Donetsk after suffering a kick on his shin by Danny Welbeck in training on Tuesday.
With Roy Hodgson due to name his squad later today for the games that will determine whether his side make it to the Finals in Brazil next year, it must have been a worry.
However, those fears have already been dispelled, with Moyes confirming he expects Rooney to be available for Saturday's Premier League trip to Sunderland.
"Wayne Rooney will be okay for Saturday," said Moyes.
"He clashed shins with Danny Welbeck (in training).
"At a push we probably could have risked him but we decided not to."
Given Rooney's impressive recent form, his absence could well have caused Moyes a problem in the Donbass Arena.
After all, Arsenal (twice), Tottenham and, last season, Chelsea had already lost in the stadium.
Given United's appalling Premier League form, the visitors seemed ripe for another defeat.
Instead, Moyes left slightly disappointed United had not claimed victory after Danny Welbeck's first-half opener had been cancelled out by Taison 14 minutes from time.
"There was a bit of disappointment we didn't see game out," said Moyes.
"But Shakhtar are a good team, with a great reputation, so I don't think it was too bad a result.
"We never play for a draw we play to win. But the players knew it was going to be a tough game and we defended very well for the majority of it.
"It wasn't the most exciting game, both teams had three points before the match and I think we both wanted to make sure we got something from the game."
With back-to-back games against Real Sociedad, who are yet to claim a point in a testing section, to come, United are already well placed to qualify.
And Ryan Giggs will have the chance to extend his record of appearing in the most number of Champions League games, including qualifiers, edging ahead of Raul as he was introduced into his 145th game when he replaced Marouane Fellaini.
"He was always going to be needed tonight because of his experience," he said.
"And he became the player who has played the most number of matches in the Champions League which is incredible."