Manchester United are in the midst of a good run of form with just one defeat in their last nine games in all competitions.
However, the 3-3 draw last time out against Everton will have stung, with United leading 2-0 at half-time and 3-2 until Dominic Calvert-Lewin found an equaliser with the last kick of the game.
Ole Gunnar Solskjaer's side come into this game with a couple of injury issues. Eric Bailly will not be back in time for the game, and will be joined on the sidelines by Paul Pogba, who is set to miss a couple more weeks.
With it being an FA Cup game, there is the potential for Solskjaer to rotate his side and there are plenty of options around the squad.
Here's who West Ham could be facing on Tuesday night.
Goalkeeper
Dean Henderson has played in United's domestic cup games so far this season, including the 3-2 win over Liverpool in the last round of the FA Cup.
With David de Gea making an error that allowed Everton back into the game on Saturday, we can expect to see Henderson starting again at Old Trafford.
Defence
One area we are likely to not see too much rotation from United is defence. In the last round against rivals Liverpool, it was a full-strength back four.
Aaron Wan-Bissaka is pretty much United's only senior right-back at the moment, with Axel Tuanzebe able to fill in on the flank. However, with Bailly unavailable, it could be more likely to see him come in for either Victor Lindelof or Harry Maguire in the centre - if Solskjaer decides to make a change at all.
One area he could rotate in defence is left-back, with Luke Shaw being offered strong competition this season following the arrival of Alex Telles. Shaw has started the last three matches following the defeat against Sheffield United, so could be rested at Old Trafford.
Midfield
With Solskjaer's side not playing again until Sunday afternoon, there is plenty of time for players to recuperate, and with how well West Ham have done this season, it is unlikely they will be underestimated.
Scott McTominay and Fred have been Solskjaer's go-to midfield for big games this season, but with it being a cup game there is a possibility that Nemanja Matic will be starting.
And in a central role, we could also be seeing Donny van de Beek getting a game. The former Ajax midfielder has struggled for game time so far this season, but it's likely he will start against David Moyes' side.
Attack
It's really a bit of a toss up for Man united over who will be featuring in attack. Edinson Cavani started against Everton, so could be rested, while Anthony Martial is likely to come back into the starting XI for one of Marcus Rashford, Mason Greenwood or Cavani.
Daniel James could also earn a start, and there's the possibility for Solskjaer to spring a surprise, too.
Amad Diallo recently joined the club after a deal was agreed at the end of the summer transfer window.
The transfer made some waves, with United agreeing a fee worth anywhere between £25million and £40million depending on various reports for a teenager who has made just four first team appearances.
The young attacker has played two Under-23s matches for United, scoring three goals and creating another three. While a start against a team in as good form as West Ham might be a step too far, it would not be the most surprising thing to see him in the squad for the FA Cup clash.
