Manchester United on red alert as underdogs chase FA Cup shocker

The Blades have built up an impressive reputation as cup fighters in recent seasons, reaching the FA Cup semi-final two seasons ago and last season reaching the last four of the League Cup.

Those successes were achieved under Nigel Clough and Adkins, who replaced Clough as manager of the League One club in June, wants to follow in his footsteps by sending United crashing to a humiliating defeat at Old Trafford.

"Manchester United should beat a League One side but that's the beauty of the FA Cup and especially the third round," Adkins said.

"There will be upsets and surprises and why can't that be us? It's the Theatre of Dreams, so why can't we dream.

"It's a game of football with three results on offer. We would be more than delighted with two of those."

Adkins, 50, who led Southampton to the Premier League as manager in 2012, has taken Sheffield United into promotion contention on the back of a run of just two defeats in eight games, which has lifted them to eighth in the League One table.

Adkins, who has also managed Reading and Scunthorpe, knows the Blades face a massive test against a United team seeking to win the competition for a record-equalling 12th time.

But the Premier League side's win over Swansea last weekend was their first win in nine games under Louis van Gaal and Adkins will look to exploit any vulnerability as the Yorkshire club, who last won the competition in 1925, seek one of their biggest results in their history.

- No fear -

"We are well aware of the massive threats Manchester United possess," he added.

"They have tremendous players and an outstanding manager but we have got to belief and go there with no fear factor.

"The club has done really well in the cup competitions in the last few seasons and this is another opportunity.

"It's a big step up but we can't be fearful. It's what we are striving for and where we want to be long-term, so let's go and enjoy the occasion."

For all United's pedigree in the Cup, they haven't lifted the trophy since beating Millwall in the 2004 final.

And beleaguered boss van Gaal is targeting a decent run to ease the pressure on his position and set up the chance of a first piece of silverware of his Old Trafford reign.

The Dutchman is expected to pick a strong side against the Blades and Spanish midfielder Ander Herrera should feature as he sets his sights on winning his first honour in English football.

"It's different to the Spanish Cup because it's more about the knockout situation," Herrera said.

"In Spain we play two legs in the cup, so it's good that it can be down to just one game here -- it makes it very emotional.

"It's a very interesting competition and I always watched it when I was in Spain. Every team has a chance to win it, which is good.

"We didn't go too far in the last FA Cup but I enjoyed the games a lot.

"It's a very enjoyable competition and a nice one that we can hopefully win this season."

Van Gaal will be without injured defenders Luke Shaw, Marcos Rojo, Antonio Valencia and Phil Jones through injury, but midfielder Jesse Lingard could return.