Marcus Rashford vs Paul McShane
19-year-old Rashford has been a sensation since making his debut in the United's Europa League game against Danish side FC Midtjylland last season. He scored two goals in that game, and that was then followed up by another brace against Arsenal a few days later.
Rashford's career has gone from strength to strength having won the FA Cup under former manager Louis Van Gaal, and also being included in England's Euro 2016 squad, making his debut for the national team just before the tournament.
Rashford could replace star striker Zlatan Ibrahimovic, with the Swede likely to be given a rest by manager Jose Mourinho after a frantic winter.
Rashford has all the makings to be a world class striker with his pace, his technique and his ability to punish defences.
Looking to keep Rashford quiet will be Paul McShane. The centre back is known for his warrior-like defending, going the extra mile to make sure his side stays in games. There have been a number of games this season where he has done just that, the game against Bristol City on Monday a prime example. This is something that McShane will need to do, if Reading are get a positive result against the cup holders.
Michael Carrick vs John Swift
The 35-year-old veteran midfielder, Michael Carrick, could return to the starting line up after returning to training following a recent injury.
Known for his ability to dictate play in midfield, Carrick will be the player the Red Devils will look to feed the ball to in order to give attacking midfielders Paul Pogba and Juan Mata the ball in attacking areas.
Carrick will also be tasked to stop any attacks from being created and making sure his side keeps possession of the ball.
Looking to cause problems for Carrick will be John Swift, the 21-year-old made his first start since returning from injury in the thrilling 3-2 win over Bristol City on Monday.
This is the perfect game for Swift to show to a big audience just how good he really his. The former Chelsea man has played a big role in Reading's rise to the play-offs with three goals and four assists. Without his contribution, Reading would probably not be where they are in the league.
If Swift can provide some sort of creativity then this will provide huge encouragement for his teammates, as the Royals look to cause an upset.
Phil Jones vs Yann Kermorgant
The 24-year-old Phil Jones has broken into the starting XI in recent weeks after returning from a knee injury.
As a result, Jones hasn't played much this season. In fact, he has only made nine appearances in all competitions, making him a likely candidate to fill one of the centre back spots.
In the nine games Jones has played, the England International has kept three clean sheets and conceded six goals.
Looking to get a sniff at the Red Devils goal will be Yann Kermorgant, a player in my view who will be key if Reading are to get a positive result at Old Trafford. The Frenchman is also in bit of form with three goals in two games, including a brace in the win over Bristol City last time out.
With his height and strength, the forward will be the man up top that Reading will look to in order to win headers and hold the ball up, allowing his teammates to join the attacks.
This is something that will be key if Reading are to cause one of the great upsets by beating the 12 times FA Cup winners in their own backyard.
For those that missed, it here's a video of Kermorgant scoring his brace in that remarkable win at Bristol City.
So there you have it. Do you agree? Will the game be decided in these areas? Leave us a comment below.