Paul Heckingbottom has told his Sheffield United side their shock win at Manchester United proves it is possible to knock Chelsea out of the FA Cup.
The Blades, the Premier League's bottom side, sprung a major surprise in January when they triumphed 2-1 at Old Trafford, inflicting the hosts' first defeat in 14 league matches.
With Heckingbottom now in caretaker charge until the end of the season following boss Chris Wilder's departure last weekend, the team on Sunday play away against a Chelsea outfit who are unbeaten in 13 matches in all competitions under manager Thomas Tuchel.
The quarter-final contest comes four days on from the Blues beating LaLiga leaders Atletico Madrid at Stamford Bridge as they advanced into the last eight of the Champions League.
Heckingbottom, who oversaw a 5-0 loss at Leicester in his first match in charge on Sunday, said: "It (Chelsea's tie against Atletico Madrid) shows the size of the task. But it's also a one-off game.
"Everyone wrote this team off before they went to Old Trafford and pulled off the win there. So we know the size of the task, but we also know it's possible. That's it, simple. If we didn't think it was possible, we may as well give them the round.
"It's a fantastic experience, a great game to play in and they don't come around very often – no matter how long your career is, quarter-finals of the FA Cup don't come around often."
Chelsea progressed to the FA Cup last eight via a 1-0 win at Heckingbottom's old club Barnsley.
And when asked about the problems the Tykes caused Tuchel's men in that tie, Heckingbottom said: "The pitch was certainly a leveller, but the biggest thing Barnsley did in that game, and the teams who have competed and made it difficult for them – it's been their energy, the willingness to play on the front foot and go and get in Chelsea's face.
"But if I'm honest, Chelsea to me have gone up another level as well, so we need more than that. We need to have that energy, we need to have that discipline, we can't be embarrassed by trying to outwork them, but also when we get the ball, we have to be good enough to hurt them as well.
"That's the emphasis and that's the message that we've been trying to work on this week."
