With Robin van Persie already ruled out for four weeks with a thigh problem, the last thing Moyes needs is to be without the man who has carried United through much of a troubled campaign.
However, when Rooney's name was missing from the squad that booked a Capital One Cup semi-final encounter with Sunderland next month thanks to a 2-0 win at Stoke, there were obvious concerns among the United support.
But Moyes insists it is nothing serious and the 28-year-old may yet play a full part in the festive programme as United look to get their Premier League campaign back on track.
"It's a groin strain," said the United boss.
Then, when asked whether Rooney could face West Ham, Moyes replied: "He has got a chance, yes."
The game was a strange affair, with little happening either side of a 10-minute break called by referee Mark Clattenburg when already heavy rain increased significantly in the swirling wind.
Clattenburg said he could not see, a view backed up by many of the players, even if the supporters felt a break was unnecessary.
Ultimately though, the match turned into a personal triumph for Ashley Young, who lashed home his first goal in over 19 months after striding on to what turned into the perfect lay-off from Javier Hernandez, and then set up Patrice Evra for a rare right-footed goal.
"I didn't know that," said Moyes, when told how long it had been since Young's last goal.
"Ashley has got the ability to score and he is a good goalscorer, we see that in training.
"He needed the goal for himself."
Young has not always been a crowd favourite at Old Trafford, where his diving antics have earned him almost as much criticism as they have amongst away fans.
Stoke's supporters were on his back earlier in the contest, even though when he did go to ground it was with good reason.
And Moyes feels his behaviour was impeccable.
"I have spoken to Ashley and I have said, make sure you do everything right. Tonight he did," said the Scot.
"He got kicked a few times and he went down, but he got back up and got on with it.
"He has shown he can come in and make an impact. That is what I need.
"We have got a lot of competition in wide areas at Manchester United, and a lot of players we can select from.
"If you want to get regular outings you need to score and you need to play well."
Moyes could not complain at the draw, which pits his team against the side currently bottom of the Premier League and whom they have already beaten at the Stadium of Light this season.
Having the second leg at Old Trafford next month provides the Red Devils with an additional advantage to seal what looks certain to be the first ever final encounter between the two Manchester clubs.
Predictably though, Moyes is adopting a cautious attitude to that prospect.
"Sunderland have just had a really good result against Chelsea and we are going to have play well over the two legs to get to the final," said Moyes.
"When the draw was made it looked like Chelsea, Tottenham, maybe us, and (Manchester) City.
"But you never know in the cup competitions. We certainly won't be taking anyone lightly in the semi-final."
For Stoke boss Mark Hughes, a disappointing evening was made worse by an groin injury to skipper Ryan Shawcross.
"We don't know how bad it is," said Hughes.
"We will have to see tomorrow. It is a big blow if we lose him because we are without Robert Huth at the moment."
As for the conditions, Hughes said he understood Clattenburg's decision to take the teams off, even if it was a unique experience for the Welshman.
"You have to accept it," said Hughes.
"The referee was saying he couldn't see.
"If you can't see you can't make decisions but I've not been involved in a game where you have had to come off and go back on."