It will be the second time David Wagner's men will have hosted the Premier League giants this season – the first seeing a memorable 2-1 victory back in October for the Terriers.
Can lightening strike twice? The German boss spoke about the chances of another upset during his pre-match press conference as well as give an injury update on the likes of Aaron Mooy, Jon Gorenc Stankovic and Laurent Depoitre.
Read all of David Wagner's thoughts in the full transcript of the pre-match press conference below...
On Town's recent goal scoring prowess...
If you look at the last two games this is the truth, apart from the goals, the boys have played with confidence and created a lot of opportunities.
We've had two very good games, not just offensively with eight goals but defensively I think we have looked very solid and focused as well.
We've put together two good results now – one in the cup and one in the Premier League, two important games and now we have another one in the cup.
On Town's overall recent performances...
It is important but what is more important is that they are able to produce these performances when they have to.
This was exactly the case in the cup where it was win-or-die and they had to produce a performance to come into the next round and in the game against AFC Bournemouth they produced a performance of the highest level.
They've done it a number of times in the past though – Play-Off semi-finals and finals, games when they were asked to show it and they delivered.
It's a top quality this dressing room has and will have to keep showing this for the rest of the season – starting tomorrow.
On Aaron Mooy's injury...
It is only a cut but unfortunately there was an infection when he got his stitches so there is a slight set-back but nothing serious.
He will miss the next two games and maybe the one against Tottenham Hotspur but then he will be back.
I am always sad when my players are injured, but there is no muscle or ligament damage and he will come back mentally and physically fresh in two weeks.
We have options even if we do not like to lose Aaron or any of our players.
On other injuries...
Three weeks ago it was great because we had everybody healthy but now we have Alex Pritchard cup-tied; Micheal Hefele ill; Chris Lowe has hamstring problems but will be back in training next week and Sean Scannell will be out for 4-6 weeks with a shoulder injury he picked up in the Under 23 game on Monday.
Jon Gorenc Stankovic is playing another 45 minutes against Barnsley for the Under 23s today as is Pritchard.
Stankovic needs time and we will not put him under any pressure and we will bring him step-by-step back to his best level.
Laurent Depoitre is also back in training and in his case there is no infection after his operation with his stitches and will be part of the squad.
On prioritising the league over the cup....
Since the start of the season the Premier League has always been the priority but this doesn't mean we don't want to be successful in other competitions as well.
For sure we like to be successful tomorrow, the players fought for 120 minutes in the replay against Birmingham City to get into the fifth round and play Manchester United at home.
We are happy, excited and glad to be involved and host them and it's a game for our supporters and a present for them.
We will try everything with our supporters to create a special FA Cup atmosphere – it's a great occasion even with the injuries we have.
On revelling in the FA Cup occasion...
It's the cup and we can play this game with freedom against one of the biggest names in world football at the John Smith's Stadium.
If there was one game we can play with total freedom it's tomorrow – we have shown in the past we can cause them some problems but we have to be on our best.
We can only win tomorrow – but we need everyone, including the supporters, to be at their best for a chance of creating something special.
On the chances of beating Manchester United (again)...
Usually if you play Manchester United three times they will not make the same mistakes twice but in football anything is possible.
On the Manchester United teamsheet...
Even if it is one of the best teams in Europe with one of the best managers in Europe we are focused on ourselves and hopefully will find a set-up that will cause them problems and create a result no-one expects.
On the forthcoming West Bromwich Albion Premier League clash...
Honestly there is nothing in the back of my head – it is all about tomorrow and we cannot work as hard as we did in the replay and then have the game a week later in the back of our head.
We want to get into the next round – however hard the task is but it doesn't mean we won't rotate but if we do rotate it is only to be successful...