United rocked by Van Persie injury
After a largely uninterrupted debut campaign with the Old Trafford outfit, Van Persie has suffered a series of setbacks this time around.
Troubled by groin and toe problems, Van Persie was making only his 16th appearance of the campaign when he was introduced as a substitute during Tuesday's Champions League win over Shakhtar Donetsk.
But the Dutchman had been on the field for only four minutes before he swung over the corner that Phil Jones' swept home for United's winner.
Elation at the goal, which confirmed United as group stage winners, was tempered by news that Van Persie had strained his thigh as he was taking the corner.
It means the 30-year-old is now set to miss Sunday's trip to Aston Villa, the entire festive programme, Wednesday's Capital One Cup quarter-final against Stoke, plus the first leg of any subsequent semi-final and the FA Cup third round encounter with Swansea on January 5.
For Moyes, who is looking to guide United back up the Premier League table after successive home losses, it is a major setback given Van Persie's status as Golden Boot winner for the past two seasons.
"It is a big blow to us," said the United boss.
"He picked up a thigh strain in taking a corner kick which led to the goal.
"It is unfortunate because if you look at our record with Wayne Rooney and Robin in the team it is actually very good and we have not had them for quite a period recently."
Although he has not reached the levels of last term, Van Persie has scored on eight occasions, most recently when he headed home the winner against his old club Arsenal on November 10.
Moyes could be forgiven for believing he was cursed given influential midfielder Michael Carrick has been missing since that Arsenal game, when he aggravated an Achilles complaint.
In addition, £27.5million new-boy Marouane Fellaini has been troubled by a wrist injury and is now laid low by a back complaint, while veteran pair Nemanja Vidic and Patrice Evra, plus England defender Chris Smalling, also missed the Shakhtar victory.
"I have no doubt it will get better," said Moyes.
"I am sure we have plenty of players who can cover it and we don't miss them too much."
If there is one silver lining for Moyes, it is that he does have plenty of offensive options available and Wayne Rooney has enjoyed a reasonably productive partnership with Shinji Kagawa when the pair have operated in tandem.
Yet United's tally of just eight goals at Old Trafford takes some explaining.
Moyes feels the absence of Carrick might have something to do with it given he failed to make the signings he wanted during the summer.
"I do (feel United have felt Carrick's loss)," said Moyes
"We need him for his creativity. We have missed him for lots of other reasons as well.
"We were looking for a couple of midfield players in the summer. We needed one who could give us something else if we did get an injury to Michael or one who could have played with him.
"We weren't able to get two. We got one so we have definitely been a little bit short in that area.
"Hopefully he is not too far away and he will be back in a couple of weeks."