"It's disappointing but there is nothing we could do about it. We had to rearrange the game and this is the earliest week we could have played it.
"With Dundee United having a game on Sunday, we couldn't really play it on Tuesday - 48 hours afterwards would have given us a massive advantage.
"So Wednesday was chosen and we didn't actually know at the time that it was clashing with the Celtic game.
"It's not ideal. It's a great spectacle, Barcelona against the Scottish champions Celtic. People might decide to sit in, in warmth and comfort. "But hopefully the genuine Motherwell and Dundee United fans will come along and see a terrific game against two sides who are hopefully hitting a bit of form now."
The Steelmen picked up a morale-boosting 3-1 win against St Johnstone, while United fought back from behind to earn a last-gasp draw against Celtic in their respective last outings. Defender Steven Hammell said: "The win on Saturday was important for us. We needed it to keep pace with the teams around us and above us.
"We go into the Dundee United game full of confidence. They might be the same, with the way they ended the Celtic game.
"It looked like they were heading for a defeat and they turned it around in the last five minutes and showed great character to get a draw.
"They will be coming here on the back of a good result as well."
United boss Peter Houston knows Fir Park has been a tough venue for his Tangerines team in the past, especially with Motherwell having recaptured form lately following a dip. And he insists they are fully prepared for the challenge which lies ahead against McCall's men. He said: "We know to expect nothing other than a very hard game.
"Stuart McCall deserves a lot of credit for the team he's built and they always like to attack. We'll have to be wary of that but, at the same time, focus on ourselves.
"We have this game followed by Hibs at the weekend but we'll concentrate on one match at a time and see where it takes us.
"The boys are in good spirits and when you've had a good result they're always eager for the next game."