The Latics have a poor record against Sir Alex Ferguson's side at Old Trafford but Martinez believes April's win at the DW Stadium gives his side a much better chance of upsetting the odds this weekend.
The 1-0 victory, which came as Wigan looked to stave off relegation, is an accomplishment Martinez is keen to remind his players of ahead of one of the toughest league games of the season.
"You need to have a visual picture. Any big achievement starts with a dream," Martinez said.
"It really helps when you have something to fall back on. Last year's performance at the DW Stadium was everything we wanted in our performance.
"We were in a very difficult position, we needed the points, and in a way we forgot who we were playing against. That's something we need to bring into this season's encounter at Old Trafford."
However, the Spaniard still expects a tough battle and admits it will be difficult to return home with any points to add to the four Wigan have already won from the three opening fixtures of the season.
"Old Trafford has been a really difficult place for us to perform and be ourselves," the Wigan boss said.
"We're looking at seven visits, 24 goals conceded and only one goal scored from a dead-ball situation - a stoppage-time penalty from Leighton Baines - so it shows how difficult it is to be yourself.
"But if there is a moment to be mentally ready to face that I think it is just now.
"The last game against United we got a well deserved win. It wasn't an accident, it was a well deserved performance and even though we know going to Old Trafford will be very different, it is a challenge that we look forward to.
"It's a great opportunity to write new history at this football club. We went to Anfield and got a win. We went to the Emirates and got a win. We went to Stamford Bridge and we were proud of our performance.
"Playing against United it can be a really tough test but we need to be ourselves and have a visual picture of last season.
"It will help from a mental point of view but clearly we need to be our best and be as strong as we can be individually."
Martinez looks set to be without defenders Jean Beausejour and Antolin Alcaraz for the meeting as both are struggling with leg problems.
Beausejour came off during the 2-2 draw against Stoke with a hamstring problem and missed Chile's two 2014 World Cup qualification games, while Alcaraz returned from international duty with Paraguay with an abductor problem.
Martinez said: "[We have] a real concern over Jean Beausejour.
"Obviously he had to come off against Stoke and miss his international commitment with Chile but he's been recovering well.
"I think he's reacted to treatment very well. I can say he will be 100% fit for the Fulham game at home [on September 22].
"Then there's a real concern over Antolin Alcaraz. He played against Argentina then had to come off against Venezuela in the 70th minute.
"He's got a soft tissue problem and we'll assess him as soon as he lands in the UK but he is a real worry."
United could be without Wayne Rooney, Robin van Persie, Shinji Kagawa and Patrice Evra for the match, but Martinez refuses to underestimate the side his team will face tomorrow afternoon.
"There's never a good time or bad time to play top teams," Martinez said.
"Manchester United are used to dealing with that kind of situation.
"I know with Manchester United, whoever is going to play will be a full international, they're going to be a group of players with an incredible winning mentality, and they are always ready to cope with any football demand."