The European champion goes into the game having suffered its first major setback of the season in Wednesday's (AEDT) Champions League game at Shakhtar Donetsk.
The 2-1 defeat came at the time of year when Chelsea has suffered a slump in three of the past four seasons that have ultimately cost it in the title race.
Defeat would raise the spectre of a repeat, but a victory would help banish those demons for a side that has already made its second-best start ever to a Premier League campaign with 22 points from 24.
Midfielder Mikel said: "All of us know what has happened in recent seasons, so we have to make sure that this defeat doesn't make that happen again.
"We have to make sure we correct it very quickly and that starts with the next game against United.
"They will be very dangerous as usual and, if we defend the way we did (against Shakhtar), it's going to be difficult for us.
"We have to defend as a unit, play together as a unit. As long as we do that on Sunday, we'll have a very good chance."
The 25-year-old controversially snubbed a move to Old Trafford to join the Blues from Lyn in 2005, leading to a bitter legal dispute.
But Mikel said of facing United once again: "There's no extra edge for me. I've got over it and I think they have got over it as well.
"It's just a normal game for me. It's going to be a great game. We have to pick ourselves up. It's going to be difficult but we have to do that."
"We have to analyse it well and see where we made the mistakes," he said. "These things are down to concentration and preparing for the game. We have to start well and be focused for the whole 90 minutes.
"This is the change of the team. We defend as a team and we attack as a team. We have to stay together and be more compact in this type of game. That makes it easier for your team-mates.
"Of course, a result like that has an effect on morale but this is one of the most crucial games of the season.
"We've had two difficult games, at Spurs and Shakhtar and now we have to recover and prepare well for Sunday."
Meanwhile, Chelsea’s vice-captain Frank Lampard will miss the crucial fixture against Manchester United and could be out for up to three weeks with the recurrence of calf injury which forced the midfielder to limp out of the club’s 1-2 Champions League defeat to Shakhtar Donetsk.
The 34-year-old lasted only 15 minutes of the game. “It's basically a recurrence of an old injury,” said Chelsea manger Roberto Di Matteo.
Newcastle Jets have been crowned Champions of the Singapore Soccer Sixes after defeating Chonburi FC of Thailand 4-1 in Sunday’s grand final.