Billy Sharp and Robin Olsen show the bottle to earn Sheffield United a win

The Sheffield United captain had been suffering as much as any of his team-mates on a day when things were just not clicking for his side, but when the opportunity presented itself from the penalty spot in the 89th minute, he thumped his kick beyond Ryan Allsop.

It secured a win that should always have been on the cards from the moment Allsop came on to replace Kelle Roos, red-carded for bringing Sharp down just outside the area after 58 minutes. The hosts had 69 per cent of the ball, allowed to dictate the game from that point on.

But try as they might, it was starting to feel like the Blades might not be able to blow the door down. Derby County's players, demoted to bottom of the table in midweek and on minus points, showed tremendous character to hang in there, and Robin Olsen was needed to tip Tom Lawrence shot onto the post as the Rams hit the woodwork for the second time in the game.

Sharp showed just as much bottle to spoil their day.

"We've got Billy Sharp, " roared the home fans making up the bulk of a 27,905.

It continued an excellent September which has seen Slavisa Jokanovic's team step up a couple of levels. But the emotions at full-time could easily have been very different.

It was clear fairly early on at Bramall Lane that things were not quite clicking for the home side.

Morgan Gibbs-White has been so inspirational for them this month but in the space of a couple of minutes around the quarter-hour mark he lost possession to set up a Derby counter-attack, broke a move down with a heavy touch, then overhit a return pass to George Baldock.

When a foul was given against him, Gibbs-White thought it should have been the other way and his protests earned him and Graeme Shinnie bookings.

Sharp was having a similarly frustrating day, beautifully taking a Baldock pass over the tp down but wellying it high and wide. He then headed a 28th-minute cross from Baldock wide.

Falling backwards he headed behind at a corner won, it must be pointed out, by some nifty Gibbs-White footwork.

So whilst the Blades had nearly two thirds of the first-half possession but the best chances were Derby's.

Marking his 700th career appearance by playing against Sheffield United at Bramall Lane for the first time, Phil Jagielka headed against the crossbar from a corner midway through the first half.

In the 37th minute Tom Lawrence had a shot blocked and it fell for Sam Baldock, playing on the same side of the field as his brother, whose snapshot flashed just wide.

Olsen had to save from Shinnie.

The half ended with a Blades chance after Ben Osborn produced a couple of stepovers and a clever pass to Sharp, whose cross Iliman Ndiaye's header could only pinball around as Osborn appealed in vain for a penalty when he tried to finish.

After 53 minutes Baldock nearly released Sharp simply by putting his foot through the ball and five minutes later a long pass from Oliver Norwood changed the complexion of the game.

Sharp and Roos ran for the ball and the goalkeeper brought his man down outside the area. David Webb blew his whistle before Osborn put the loose ball into the net.

From there it became a game of defence versus attack, Jokanovic throwing Oli McBurnie on as a second striker and turning Baldock and substitute Enda Stevens into full-blown wing-backs.

As Ndiaye's shot deflected wide and put his header from a Gibbs-White cross five yards wide, Gibbs-White volleyed wide at a corner, Baldock and Stevens both blazed over, and Osborn's shot deflected above the post, it felt like it was not going to be their side's day.

Then, inexplicably, Curtis Davies palmed away a cross by substitute Conor Hourihane and Sharp smashed the ball down the middle.

Still there could have been a late twist when Lawrence and Olsen went head-to-head right at the death.

Having worked so hard to finally get in front, the Blades were not about to be denied.

Sheffield United: Olsen; Baldock, Egan, Davies, Norrington-Davies (Stevens 71); Norwood (McBurnie 66), Fleck; Gibbs-White, Ndiaye (Hourihane 81), Osborn; Sharp.

Unused substitutes: Basham, Brewster, Foderingham, Guedioura.

Derby County: Roos; Byrne, Jagielka, Davies, Buchanan; Bird, Shinnie; Sibley (Allsop 58, Baldock (Jozwiak 65); Lawrence), Morrison (Knight 58).

Unused substitutes: Forsyth, Stearman, Stretton, Watson.

Referee: D Webb (County Durham).