Image source, PA

With West Ham and West Brom circling, tonight could well be midfielder Darren Fletcher's final game for Manchester United after 12 years in the first-team squad. He is on the bench.

Interestingly, the 30-year-old is the only remaining member of the Manchester United squad to have won the FA Cup. Fletcher was part of the side which beat Millwall 3-0 in 2004 - United's last victory.

Former Cambridge United and Manchester United striker Dion Dublin

"When you mention Cambridge these days people don't really think of football - they think of education and intelligent people. Over the period of my four years here with the motley crew I played with, football was pretty much top of the list. It was a small club that hadn't really achieved that much, in Division Four at the time, we didn't really know what would happen. But all the players in that squad - people like Steve Claridge, Liam Daish, Lee Philpott - had the same drive and work ethic."

Man Utd

There is no Wayne Rooney in the Manchester United squad. Louis van Gaal makes three changes from the side which started at QPR last weekend, Adnan Januzaj is back and goalscorers Marouane Fellaini and James Wilson both start.

Man Utd XI: De Gea, Jones, Rojo, Blind, Valencia, Carrick, Fellaini, Januzaj, Di Maria, Wilson, Falcao

BBC Sport chief football writer Phil McNulty

"Cambridge Head Coach Richard Money knows the odds are against his League Two side but this experienced figure has seen enough of the FA Cup not to dismiss his side's chances, even against Manchester United.

"In his programme notes he writes: "I have no idea what percentage of a chance anyone in their right mind would give us. But however small that percentage is it definitely isn't zero."

Image source, EPA

Manchester United manager Louis van Gaal insists he is not taking Cambridge, who are 12th in League Two, lightly.

"Cambridge play very direct, with long balls," said the Dutchman. "They have five or six players above 1m 90cm [6ft 3in] so for us it's difficult to defend and that's why you have to prepare yourself very well.

"It's not so easy to beat Cambridge United.

"On Wednesday PSV Eindhoven, who are top of the first league [the Eredivisie] in the Netherlands, lost against the third team of the second division, Roda JC. Ajax, Feyenoord and PSV are out [of the KNVB Cup]. That's remarkable.

"Surprises shall happen also in the FA Cup. There are always surprises and I hope we are not the surprise. It's another opponent with another playing style with other players and we have to beat them."

With 75 league positions, 70-odd thousand seats and millions and millions of pounds between Cambridge and Manchester United, a home win tonight would go down as one of the biggest Cupsets in living memory.

We've discussed the best FA Cup shocks a lot this season - but what is the most surprised you've ever been at another, non-football sporting moment?

Image source, Getty Images

Could you not believe your eyes when Usain Bolt false-started at the world championships? Left mute when Rafa Nadal was knocked out at Wimbledon early doors? Stunned by Mon Mome winning the National?

Get in touch at #bbcfacup, external, pop on to the BBC Sport Facebook page, external or BBC Sport's Google+ area., external

You can also text us on 81111 in the UK only - don't forget to say who you are and where you are texting from.

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These sides have met before on just two occasions - both legs of a League Cup tie in 1991.

Manchester United won the first leg 3-0 thanks to goals from a 17-year old Ryan Giggs, Steve Bruce and Brian McClair. The second leg at the Abbey Stadium was drawn 1-1. Future Man Utd striker Dion Dublin scored for Cambridge while McClair was again on the scoresheet for the Red Devils.

I couldn't find a picture of Dion bagging in that game but here he is at future home Highfield Road. Magnificent.

Image source, Getty Images

Are you the loudest voice in the stands at your club's matches? Well this one might be for you...

BBC Sport has teamed up with Songs of Praise to offer a fans' choir the chance to sing 'Abide With Me' before the 2015 FA Cup final at Wembley in May.

The choir will be made up of one fan from each of the 64 teams which made it to the third round.

Applicants need to go here to enter.

Queens Park Rangers defender Rio Ferdinand

Image source, Getty Images

"I'm going for 3-0 to Manchester United in this FA Cup tie. Watch out for Sullay Kaikai (on loan from Crystal Palace) for Cambridge United."

Image source, Getty Images

Ghana and Crystal Palace forward Kwesi Appiah scored six goals in 19 league appearances on loan at Cambridge this season - and two more in the cup. His stay at the Abbey Stadium came to an end on 10 January, but he sent this message to his former team-mates from the Africa Cup of Nations, via the BBC World Service.

"Sorry I can't be there to support you or play, but good luck guys - you can do it. There are always big shocks in the FA Cup so why not be one of them?"

That's the spirit Dion!

Former Cambridge United and Manchester United striker Dion Dublin

"The FA Cup nights when I played at Cambridge United were special - the stands were jam packed, there wasn't a spare seat or place on the terrace to be had. We just seemed to roll teams over with shear power and determination. And when we'd win games the supporters would be straight on the pitch. Manchester United will play the way they do, but this game is at the Abbey Stadium. Anything can happen!"

Can Cambridge cause a shock or will Manchester United simply be too strong?

Have your say now by voting at the top of this page. The vote will close at 19:45 GMT and terms and conditions can be found here.

Wayne Rooney, Angel Di Maria and Radamel Falcao have seen the world playing football - but have they ever had to make their way through a bovine gauntlet to get to the ground?

At the Abbey Stadium, entrance to the South Stand, which houses away supporters, is through Coldham's Common. Between April and November it is home to dozens of English Longhorn cows.

It is not unusual in Cambridge, where cattle owners can receive permission to graze their livestock on the public commons. The Commons Registration Act of 1965 states that Coldham's Common can hold "geldings, mares and cows to a total of 124 beasts".

"I've run through cows in pre-season," said ex-Cambridge striker John Taylor. "It was OK as long as they stayed away from me. I was petrified of them. Cows are too big, aren't they?"

They are John. Massive.

Cambridge are unbeaten so far in 2015 and are not bereft of players that can play. Former England youth international Ryan Donaldson scored three goals at Wembley last season, Crystal Palace youngster Sullay Kaikai is a box of tricks while Norwich's on-loan prodigy Cameron McGeehan scored twice on his debut on Saturday and has "a terrible habit of giving the ball to someone with the same shirt" according to U's boss Richard Money.

Image source, EPA

Speaking of money, Cambridge's wage bill last year was reportedly a mere £1.25m. Wayne Rooney earns that in just over a month and the Red Devils' total for last season stood at a whopping £214.8m. In the true spirit of the FA Cup, this a real David v Goliath encounter.

Former Manchester United striker Dion Dublin
BBC World Service

"Everything is going to be different for the Manchester United players. The changing rooms aren't big, and they will have to bob their head down to go down the corridor that takes them to the pitch. It's down to the individual to respect where they are going to and where those Cambridge players are trying to get to.

"You've got to go there and say: 'In order to beat them we are going to have to be at the top of our game'. I think United will have too much quality but it's applying that quality on the day. Cambridge will come out absolutely flying."

Think of football in Cambridge and you probably think of (if anything) long ball, hoofs, Dion Dublin, Fever Pitch, long grass and dodgy gamesmanship.

John Beck's side of the late 1980s and early 1990s produced nothing short of a miracle - climbing the footballing ladder from Division Four to the play-offs in what is now the Championship. All of that on a shoestring budget, in a tiny ground and with nothing but contempt from outsiders who sneered at their approach.

Image source, Empics

"John Beck kept the grass in the corner long, put a bit of sand in the corners," recalls Cambridge's record goalscorer John "Shaggy" Taylor.

"We had cold water thrown over us before the game to wake us up. He knew there was a reason for it.

"Some of the things were a bit quirky. But people couldn't handle the way we played."

Quite right too. Can the current side produce more miracles tonight?

Dan Walker
BBC Sport

"I believe this is the 'Urinal of Dreams'

Image source, @mrdanwalker

Manchester United have arrived at Cambridge and Louis van Gaal has been out on the pitch, checking it out. I've seen reports that there is no Wayne Rooney tonight but that is as yet unconfirmed. Full team news should be with you in around 15 minutes.

BBC Sport chief football writer Phil McNulty at the Abbey Stadium

"It's another FA Cup trip into the unknown for Manchester United manager Louis Van Gaal. The third round took him to Somerset and a meeting with Yeovil - the fourth has him here at the Abbey Stadium to face Cambridge United.

"Cambridge are 76 places below United but - in front of a national television audience - what an opportunity for Richard Money and his players to write their name into folklore.

"Freezing temperatures here just off Newmarket Road - but Yeovil provided the perfect dress rehearsal for Van Gaal for tonight's test."