United's 2-2 draw with Well last Sunday added to their fixture congestion but kept their hopes of a successful defence of the Scottish Cup alive. The replay had been scheduled for March 29, just two days after Scotland's friendly with Brazil at the Emirates Stadium.
However, now United manager Peter Houston, who is the Scotland assistant boss, has been given an extra day to prepare his side for the match.
Houston was unsure an alternative date for the match could be found and was unfazed by the prospect of the initial March 29 date.
He said: "We haven't got dates for it, so unless Motherwell look to change it... but I don't know when we'll be able to fit it in.
"We know Motherwell exceptionally well. All we'll be doing is working on our own team shape."
With the Clydesdale Bank Premier League split approaching, games continue to come thick and fast and following the Scottish Cup replay at Fir Park - the winners of which will take on Brechin or St Johnstone in the semi-final - United are scheduled to play Rangers, Motherwell and then St Johnstone.
First, United, who are in the midst of a run of five games in 12 days, all at home, play Hearts on Wednesday and Inverness on Saturday.
Houston, who will be hopeful Wednesday's match survives the weather after torrential and persistent rain fell in the east of Scotland today, said: "We want to look at the next two games, try to take some points from that.
"We're going to give the guys three or four days off next week because they've earned it and deserve it."
Source: PA
Source: PA