Tottenham assistant head coach Cristian Stellini apologised to the club’s fans after they were dumped out of the FA Cup by Sheffield United.

Blades substitute Iliman Ndiaye’s solitary second-half strike clinched the Sky Bet Championship promotion-chasers a home quarter-final tie against Blackburn.

Tottenham’s wait for a major trophy continues – they won the League Cup in 2008 – and they have now exited the FA Cup at the fifth-round stage three times in the last four years.

Head coach Antonio Conte missed his side’s latest exit as he recovers from gallbladder surgery and Stellini said: “I think we missed a big opportunity and we have to apologise to the fans.

“There were 5,000 of them here to watch our performance and we apologise because we missed a big opportunity.”

The closest Tottenham came to scoring was in the first half through Lucas Moura’s cross-shot which skimmed the bar, while 65th-minute substitute Harry Kane headed Ivan Perisic’s stoppage-time cross wide.

Stellini made six changes after Sunday’s win against Chelsea and revealed England skipper Kane had been struggling with illness.

“I think the team we chose to play the game was fine,” Stellini said. “We used a good team to play this game against this type of opponent. The problem was the energy.

“When the energy is not at the same level as your opponent sometimes you can lose. We had the opportunity to score, but we never found the target.”

Kane, who missed last month’s win at Fulham through illness, scored in Sunday’s 2-0 win against Chelsea, which lifted them up to fourth in the Premier League.

Stellini insisted it was the right decision to start with Kane on the bench at Bramall Lane.

“It is not a regret,” the Italian added. “We need to look in the medium period, we have many games.

“Harry Kane played in the last six games, one time with fever, one time with a problem. We have to take care of our best player.

“It’s not about Harry (the defeat) because we played with Richarlison, Lucas Moura and Sonny (Son Heung-min).

“I think it is good enough to play in this competition and against this sort of team.”

Blades boss Paul Heckingbottom hailed match-winner Ndiaye after the Senegal forward danced round three Tottenham defenders in the 79th minute to drill home his 11th goal of the season in all competitions.

Heckingbottom, whose side have reached the FA Cup’s last eight three times in the last four years, said: “You don’t expect anything else (from Ndiaye) – I’m just pleased he’s got his goal.

“Things have dried up a little bit for him, but we know what he still brings us every single game.

“He’s probably shown a slightly different audience what he can do with another top goal. He can do it against anyone.

“He’s unbelievable with the ball, there’s not many Premier League players who can do what he does with the ball. His standout quality is his agility with the ball.”

Heckingbottom watched from the gantry after starting a three-match touchline ban for his recent dismissal against Middlesbrough.

“The players made it a good watch for me,” he added. “I was looking forward to the game for a lot of reasons, but I was also dreading it for not being on the sidelines.

“But they made it a good watch for me so I thank them for that.”