Betting expert Joe Ross from www.footyinsider.co.uk said:
'The cynics will be adding 2 and 2 and getting five. Whilst there have been rumours in Manchester that Van Persie is not at ease with the Moyes regime, when he has played there has been no sign of that.
'We would still fancy him to be at the club come May and end up top scorer ahead of Rooney. the only fly in the ointment would be if he was ruled out for longer and United have to bring another striker in. But the injury doesn't sound that serious.'
The Dutchman, 30, was injured while taking the corner that led to Phil Jones' winner against Champions League opponents Shakhtar Donetsk on Tuesday.
United play eight matches before facing Chelsea in the league on 19 January.
"It's unfortunate," said boss David Moyes. "Our record is good with Wayne Rooney and Robin in the team. We've not had them for quite a period recently."
Van Persie has endured a campaign disrupted by injury so far after suffering toe and groin problems. Last weekend, he had returned from a month-long absence in the 1-0 defeat to Newcastle.
He arrived at Old Trafford for £24m from Arsenal in August 2012 and scored 26 goals last season as United claimed the Premier League title.
Manchester United's record with Van Persie in 2013-14: Played 16, Won 9, Lost 3, Drawn 4
Manchester United's record without Van Persie in 2013-14: Played 8, Won 4, Lost 2, Drawn 2