It may have been a key negotiating point of the deal, but if Zaha wants to switch to Old Trafford early, ultimately it is his choice.
With the opportunity to feature against, or purely just attend and soak up the atmosphere versus Real Madrid in the Champions League on offer, it's a no-brainer.
From United's point of view it makes sense too, as Ashley Young has been ruled out for six weeks with a knee injury.
With both Nani and Antonio Valencia struggling for form, and Nani only just returned from injury himself, the Red Devils are hardly blessed on the wing at the moment.
Zaha would not only shake things up at the club, but he would provide a crucial extra option for the club.
Against Madrid, assuming they start both Nani and Valencia on either side, their only like for like option will be to bring Ryan Giggs on off the bench. But what if they had Zaha available?
The 20-year-old is likely to show no fear, and Madrid while they will have done their scouting, won't know entirely what to expect. He could be a gamechanger and instant hero. Why not let him try?
If Nani and or Valencia too suffer injuries ahead of the tie, loaning Zaha out could be an unwise move.
United are paying Palace enough money, £10 million rising to £15 million, that they don't need to be overly-generous.
It will be interesting to see whether United name Zaha in their Champions League squad ahead of February's knockout ties, because if he is at Palace and is named, then it will indicate there is an option he can be recalled in case of emergency.
Being under 21 does not mean he is eligible regardless, that only counts if the player has been at the club for two years, so if they want to use him they will have to include him in their 25.
Once Zaha signs on the dotted line, he can plead his case with Sir Alex Ferguson to renege on the agreement and let him stay.
With Young injured, the picture has changed, and he could be vital. Can you imagine him sitting at home watching United take on Madrid, knowing he could be there?
Unless he really would be playing against the likes of Barnsley and Burnley instead. Would that really be best for his development?
With Young injured, should United cancel the loan option and keep Zaha?
image: © jamesboyes