League One Tranmere shocked Premier League Watford in an FA Cup third-round replay to set up a tie against 12-time winners Manchester United.

In a game rescheduled from earlier in the month because of a waterlogged pitch, Rovers capitalised on a hugely under-strength Hornets and best navigated a dire, sand-covered Prenton Park surface to finally settle the tie in extra time.

Substitute striker Paul Mullin, who came off the bench to score a late penalty at Vicarage Road and complete a remarkable Rovers comeback from 3-0 down to set up this replay, went one better with a headed winner 14 minutes into the extra 30.

The Hornets had come back themselves in normal time, with Kaylen Hinds firing in through a mass of players to level after Emmanuel Monthe had given the home side the lead.

The silver lining for Nigel Pearson's side is that they will not have to play what would have been a fourth game in nine days in the fourth round on Sunday, and will instead be able to focus all their efforts on avoiding relegation from the top flight.

Tranmere, though, get to do this all over again at the weekend, hosting Manchester United with an even greater shock in mind and on a pitch unlike any other the Red Devils will have played on this campaign.

Rovers dig deep again

This FA Cup run has been something to savour in what has been an otherwise tough season back in League One for Tranmere.

The club have been on an upward trajectory over the past two campaigns, returning to the Football League in 2018-19 after three seasons in the National League and then following that up with a second successive promotion to the third tier.

But they have won just five of 25 league games since then and sit 21st in the League One table.

However, both the original tie and this replay have showcased the battling spirit that Micky Mellon has instilled in his players. And on a sandy, rapidly deteriorating surface such as this, that appetite for battle was key.

They won tackles, stuck a boot in where their opponents would not and remained alive to the opportunities that chaos can create in a minefield of a penalty area.

Blackett-Taylor and 37-year-old veteran midfielder Neil Danns both went close before defender Monthe - also a scorer in the original tie - struck his opener in the first half, and they did not wilt when Watford levelled in the second.

They could easily have won the tie in normal time, but Mullin hit the outside of the post from a tight angle and Danns fired just past the far post with seconds left.

They were not to be denied, though, as Mullin timed his run to perfection to meet a flicked on cross from Liam Ridehalgh and head his side into the fourth round.

Second-string Hornets stung

Precariously placed in the Premier League and having just lost at relegation rivals Villa, this was a game Watford could have done without, and one they should have avoided in the first place.

Leading 3-0 at half-time in the original fixture at Vicarage Road, their place in round four was essentially booked, before their second-half capitulation allowed Tranmere parity and a replay.

When the elements then intervened and the game on 14 January was postponed, it left the Hornets facing a horror run of fixtures at a crucial juncture in their season.

No wonder then that Nigel Pearson opted to make so many changes from the defeat at Villa, with Christian Kabasele, Jose Holebas and Andre Gray the most recognisable first-team figures in a team largely comprised of under-23 players.

As an indication of how deeply the Watford boss dug into his squad, the average shirt number for the 18 named in the match-day squad was 38, with the highest on display the 72 sported by unused substitute Andi Janjeva.

None of them particularly covered themselves in glory, never fully getting to grips with their opponents or environment.

Teenage Brazilian forward Joao Pedro showed the briefest of flashes and drew a good save out of home keeper Scott Davies, who was also called into action to superbly palm away a curling Callum Whelan shot in extra time, while Holebas hit the post with an angled drive.

But these were rare moments of attacking flair in an encounter that will be quickly forgotten if the returning first team can return to winning ways in the league in nine days' time.

An unenviable task for Man Utd

Ole Gunnar Solskjaer's side will not relish the prospect of facing Tranmere on this pitch.

The FA Cup represents one of United's main potential avenues to silverware this season and you would therefore expect Solskjaer to field a stronger XI than Watford did for this game.

But they will face the same, alien problems of inconsistent bounce and roll on a surface that is as much sand as grass.

Plus, they come into the tie at arguably the lowest moment of Solskjaer's time at the club, having meekly lost their last two games - at fierce rivals Liverpool and then at home against Burnley.

Clearly, Solskjaer has the superior players at his disposal but Tranmere will have the bit between their teeth and a leveller beneath their feet.

Man of the match - Emmanuel Monthe (Tranmere)

What's next?

Tranmere welcome Manchester United to Prenton Park for the fourth-round tie, kicking off at 15:00 GMT on Sunday. Watford get a short break from action to lick their wounds before hosting Everton in the Premier League on Saturday, 1 February.