Manager Sir Alex Ferguson cited fatigue after his side surrendered a two-goal lead in their FA Cup quarter-final against Chelsea last week and were forced to settle for a draw.
United had gone into the that game on the back of a controversial and emotionally-draining Champions League loss to Real Madrid.
Ferguson responded by giving his players two days off to freshen up ahead of Saturday's Barclays Premier League clash with struggling Reading.
Robson expects that to pay dividends as United look to protect their healthy 12-point lead over champions and rivals Manchester City at the top of the table.
Former United captain Robson said: "I do think you sometimes have a backlash to a game like the Madrid one.
"It was such a 'charisma' game - the boys got so hyped up for it. Everybody was really up for it, so mentally and physically that can drain you a lot.
"I think a bit of that maybe came back on to us in the Chelsea game.
"But with a free week leading up to the Reading game, I don't think there will be any backlash in terms of mental fatigue from now on.
"I think the boys are full off confidence and are right up for the games ahead.
"They know how important it is to try to get the title back off City."
Robson, 56, was at Old Trafford this week to promote the Red Heart United charity game between United and Real Madrid legends at the ground on June 2.
Reading's visit on Saturday evening will be United's fourth successive home game after the 4-0 victory over Norwich a fortnight ago and the Real and Chelsea matches.
The Royals, who are four points adrift of safety, are likely to be in the caretaker control of academy coach Eamonn Dolan following Brian McDermott's departure earlier this week.
City are in action earlier in the day, attempting to cut the gap at the top to nine points, in a lunchtime kick-off at Everton.