Non-league Wrexham will believe they can shock Sheffield United in today's FA Cup clash. 

After all, Phil Parkinson's side have already knocked out Championship opposition, beating Coventry 4-3 in the previous round. 

The National League leaders are enjoying a magnificent season, winning 20 and losing just two of their 27 matches in England's fifth tier. 

Ahead of their fourth-round meeting with the Blades, we look at how the Welsh outfit can pull off another upset.

The power of Parkinson

Parkinson's men come into this clash off the back of a sixth straight league victory, having beaten Gateshead 3-0 on Tuesday — and the Wrexham manager is thrilled at the prospect of another FA Cup outing. 

He said: "For me, the FA Cup has been a great bonus for us. 

"We have enjoyed this journey we have been on but I only enjoy it if we go into those games on the back of a win, I really do. 

"Now, we can give the boys a bit of a breather because we have had two tough away games and come back in later in the week ready to do ourselves justice at the weekend. 

"Moments like that when you are on Match of the Day [after beating Coventry], an iconic football show, and you are first on it, it is great for the area, great for the club and great for the owners. 

"Rob McElhenney and Ryan Reynolds deserve that and I am sure they will be watching with great interest on Sunday." 

The 55-year-old coach has plenty of cup pedigree, having taken Bradford City to the League Cup final while they were a League Two club in 2012-13 — beating Watford, Arsenal and Aston Villa on their path to Wembley. 

He also famously knocked Chelsea and Sunderland out of the FA Cup with the Bantams in 2014-15, so will be hoping for similar heroics from his team this afternoon.

Mullin magic

Star striker Paul Mullin could be key to Wrexham's hopes of reaching the fifth round. 

The Red Dragons' talisman, 28, is reportedly among the National League's highest-paid players — but he is certainly earning his keep. 

Mullin is Wrexham's top scorer, netting a whopping 27 times in 32 appearances across all competitions.

He is the FA Cup's leading scorer from the first round onwards with six goals — and that is before you factor in his fourth qualifying round effort against Blyth Spartans. 

If anyone in Parkinson's squad can breach the Championship's tightest defence, it surely has to be the man from Merseyside.

Aerial threat

The razor-sharp Mullin is not Wrexham's only route to goal, however. 

Centre-back Ben Tozer is renowned for a catapult-like long throw — and in the towering No9 Ollie Palmer, he has the perfect target to aim for. 

Palmer is the club's second-highest scorer with 14 strikes to his name and could benefit from his team-mate's unusual wide deliveries. 

The 31-year-old centre forward has played a more limited role in Wrexham's FA Cup run so far despite netting a crucial goal in the replay against Blyth Spartans. 

But the same cannot be said for Tozer, who has started all five of their cup ties to date. 

The centre-back, 32, sees a great deal of the ball and helps his side take control of games when in possession. He will be crucial to settling his team down against a strong opponent.

Hayden heroics

As impressive as the multi-talented Tozer is, his centre-back partner Aaron Hayden shines even brighter. 

Despite playing at the heart of defence, the 26-year-old is the club's third-highest scorer with 12 in 26 league outings. 

He has yet to get on the scoresheet in the FA Cup this term but Paul Heckingbottom's unit would do well to be wary of the threat he poses. 

Between Hayden and Palmer, Wrexham boast two sizeable targets from set-piece situations — an avenue they may well look to exploit.

Ndiaye danger

For all of the Red Dragons' attacking arsenal, shutting down one of Sheffield United's star men will be equally important to their chances of progression. 

Iliman Ndiaye, 22, has been among the Championship's top performers this season, leading to reported transfer interest from Premier League strugglers Everton. 

It is not hard to see why the Senegal international is turning heads. No player in the second tier has racked up more goal contributions (17), with 10 league goals and seven assists to his name. 

Wrexham will have a job on their hands containing the Blades' dynamic forward — but minimising his impact could be key to securing a headline-grabbing victory.