A win for Leicester will confirm their spot in the top four, whilst Ole Gunnar Solskjaer's side only need to avoid defeat, however eyes will also be on events at Stamford Bridge as a defeat for Chelsea against Wolverhampton Wanderers means that both the Foxes and Red Devils could be celebrating a top four spot with a draw in the East Midlands.
Brendan Rodgers' side have struggled for form since returning to action and enter the game off the back of a 3-0 loss away to Tottenham Hotspur whilst Manchester United failed to take advantage of the Foxes' woes after being held to a 1-1 draw at home to West Ham United on Wednesday.
Bruno Fernandes has been nothing short of superb since his January arrival from Sporting Lisbon. The Portugal international has seven goals and seven assists in 13 appearances and his partnership alongside Paul Pogba in recent weeks has given opposition players more than one headache to contend with.
Wilfried Ndidi meanwhile has been a consistent performer throughout the campaign for Leicester, with the Nigerian currently second behind United right-back Aaron Wan-Bissaka for the most tackles in the Premier League this season.
If one can keep the other at bay, it could have a huge say in which side picks up a crucial three points.
Last Time Out
The earlier meeting between the two sides back in September saw them separated by a first-half Marcus Rashford penalty to inflict a first defeat of the season onto Leicester.
Rashford, who won the penalty after being fouled by Caglar Soyuncu, almost doubled his tally in the second-half with a 30-yard free-kick, however his effort cannoned off the crossbar.
The away side had chances of their own through James Maddison however the United backline - which included former Fox Harry Maguire stood tall and wouldn't allow Leicester a way back into the game.
Marc Albrighton will face a late fitness test on Sunday to see if he will be considered for selection.
The Foxes wide-man sat out the win against Sheffield United and the defeat against Tottenham but could be back in time for a place in the squad.
James Maddison, Ben Chilwell, Christian Fuchs, Ricardo Pereira and Caglar Soyuncu meanwhile will all continue to miss out due to injury.
Luke Shaw and Eric Bailly are doubts for Manchester United whilst Aaron Wan-Bissaka will definitely feature after sitting out of Wednesday's draw with West Ham with a knock. Axel Tuanzebe and Phil Jones however will play no role as they continue to sit out on the sidelines.
Leicester City: Schmeichel; Bennett, Morgan, Evans; Thomas, Tielemans, Ndidi, Justin; Barnes, Vardy, Perez.
Manchester United: De Gea; Wan-Bissaka, Lindelof, Maguire, Williams; Matic, Pogba; Greenwood, Fernandes, Rashford; Martial.
Leicester boss Brendan Rodgers has promised supporters of Leicester that his squad will be at full focus and that they can be proud of their team no matter what the outcome at full-time is.
He said: “We want to be in it, and we’ll do everything we can.
“But if we fall short, then it’s still been a brilliant season. It’s a very exciting moment for us.
“I couldn’t have asked any more from the players. But, now you have a chance to make a result that will be seen around the world.”
There’s so much to play for.”
Manchester United boss Ole Gunnar Solskjaer on the other hand has told his side they must enter Sunday's fixture with a positive mindset and to prepare for a tough game in the East Midlands.
Solskjaer said: "We have to go into the game with a positive mindset, going there to attack, going there to win the ball, going there on the front foot, defend on the front foot.
"We know Leicester are a good side and they're going to pin us back at times and we're going to have to defend our box as well, so stop crosses, if the crosses come into the box get first to it. All the basics in football.
"I just want to see them do what they've done over the last five or six weeks, go out there with a smile, express themselves, play with no fear, play with courage, go and attack teams, go and drive at them, create chances and defend well, like we have done."