After out-playing Aston Villa to win 2-0 on the opening day of the season the Latics were caught out by a pumped up Wolves team on Tuesday, conceding a sixth-minute goal which cost them dearly.
With United slipping to a shock defeat at Burnley 24 hours later Martinez knows his players cannot afford to be similarly off their game against the Barclays Premier League champions.
"We will learn a lot from the Wolves game but this is a totally different scenario," he said. "We came in to play at home (against Wolves) with great expectations after the result at the weekend and that is something new for us.
"Physically we need to recover but also mentally. The players need to get back to the levels that they need to be able to enjoy their football and perform. Obviously Manchester United are one of the best teams in the world and they will test us.
"It is important we are as good as we can be and we couldn't be like that against Wolves and that is disappointing and frustrating. But you learn a lot more from these situations and it is going to be a great lesson for us to keep improving."