How typically Tottenham to launch a pioneering new collaboration with Formula One by resting Harry Kane and crashing out of the FA Cup at Sheffield United to leave their season careering off track once again.

Just as it seemed they were finding some sort of rhythm at the right time, with victories against Chelsea and Manchester City to climb back into the top four of the Premier League and Antonio Conte expected back soon after gallbladder surgery.

Then this. Complacency in South Yorkshire. With Kane on the bench for 65 minutes, and others rested, Conte and his assistant Cristian Stellini must have hoped they could ease past Championship opponents without taking too much out of key players.

'The problem was energy,' said Stellini, who said there were no regrets about Kane. 'He was ill one week ago and didn't train some days.

'The team we chose to play was fine. We used a good team to play this game against this type of opponent. It's not about motivation. When the energy is not at the same level as your opponent sometimes you can lose. This is about mentality.'

Iliman Ndiaye broke the deadlock with a superb mazy run in the 79th minute for Sheffield Utd

By the time the England captain came on, the Blades could sense an upset.

They were kicking towards the Kop with their fans revving up the atmosphere and it was Iliman Ndiaye not Kane who turned out to be the substitute with the magic touch, firing the Blades into a quarter final, at home against Blackburn.

Ndiaye, a gifted Senegal international signed from Boreham Wood who played against England at the World Cup, struck in the 79th minute, with a brilliant goal, collecting a loose ball from a blocked cross, wriggling into a crowded penalty area and hitting a low shot through the legs of Eric Dier to beat Fraser Forster at his near post.

'You don't expect anything else,' said Blades boss Paul Heckingbottom. 'Things have dried up a little bit for him but we know what he brings and he's shown a slightly different audience what he can do with another top goal.

'Iliman can do it against anyone, agility on the ball in tight areas at the top end of the pitch, where the best players do damage. He's got all that.'

Bramall Lane erupted. Like Conte, Heckingbottom had made wholesale changes, replacing eight of the team that started the win against Watford last time out.

They too have had sickness in the camp. Centre half John Egan was suspended and they had to absorb pressure with Lucas Moura flickering on the right wing in the early stages.

Richarlison dashed onto a pass by Davinson Sanchez and fired over from the angle. Everyone turned to the assistant referee but there was no flag, he had been onside and it was an excellent opportunity wasted as the Blades resisted.

Heckingbottom's side worked hard without the ball and deserved their luck when Moura, growing in confidence dribbled into the penalty area from the Spurs right, jinked past Jack Robinson and clipped a cross towards the far post.

The ball cleared 'keeper Wes Foderingham, drifted towards goal and glanced the bar before it could be scrambled away.

Having dominated, Tottenham almost gave their hosts the lead with carelessness at the back on the brink of half time. Sanchez lost an aerial duel with Billy Sharp and Pierre-Emile Hojbjerg left a header short as he tried to find 'keeper Forster.

It left Ismaila Coulibaly clean through on an angle but the 22-year-old midfielder, making only his second start for Sheffield United, could not make it count, pulling his attempt awkwardly wide of the near post.

Ivan Perisic headed into the gloves of Foderingham from an inswinging corner after the interval and Son Heung-min stirred, flashing a curling drive narrowly over from 20 yards but they could not unlock the Blades.

Heckingbottom, looking down from his seat in the TV gantry, sent down a message to his coaching staff Stuart McCall and Jack Lester that it was time to send on some of the first team regulars, starting with Sander Berge and Max Lowe.

Spurs responded by sending on Kane and Dejan Kulusevski. The tie opened up as the two teams searched for a goal. Then came Ndiaye to win it.