Cristian Stellini apologised for a lack of effort from Tottenham after they were thrashed 4-1 at Leicester on Antonio Conte's return to the dugout.
Less than a week after Spurs were at their best to see off Manchester City at the Tottenham Hotspur Stadium - a match Conte missed as he recuperated from an operation - they were outplayed and outfought at the King Power, with James Maddison and Harvey Barnes masterminding the home side's victory.
"We have to continue to play with the same desire we had in the last game, and to be more consistent on that," assistant Stellini, who has deputised in Conte's absence, told Sky Sports. "We started well and scored, but after that we probably thought it was a bit easier than normal.
"A game is never easy to play, and after that we have to apologise. The effort and our strength went down."
Spurs' early lead came from Bentancur stabbing home a loose ball from a corner after 14 minutes, but the game was turned on its head in the blink of an eye. A goal-of-the-season contender from Nampalys Mendy pulled them level, before James Maddison slotted them in front moments later.
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A fine Kelechi Iheanacho strike on the stroke of half-time cemented Leicester's advantage, and after Spurs offered little improvement in the second 45 minutes, the hosts rounded off a fine afternoon with Harvey Barnes' pinpoint finish into the bottom corner sealing a deserved thrashing at the King Power Stadium.
Spurs' wretched afternoon was compounded by a potentially serious injury to goalscorer Bentancur, who was forced off midway through the second period.
"It happened last season too - we beat Man City, then we lost to Burnley," Stellinig added. "We have to be better in this aspect, if you beat Man City you have to continue in the next game."
How resurgent Leicester ruined Conte's return
Tottenham arrived at the King Power Stadium buoyed not only by last weekend's sensational victory over the league champions, but also the return of Conte on the back of his successful recovery from gall bladder surgery.
The Spurs boss had been told to take it easy - but what he watched unfold in the East Midlands would have been difficult to stomach.
Things had started well, Spurs taking advantage of a strong start as Bentancur bundled home a corner from a few yards out, moments after January arrival Victor Kristiansen had somehow cleared over the bar from his own goal-line.
From that point, though, stress levels began to rise in the away dugout. Leicester levelled from their first corner of the afternoon 10 minutes later, with Mendy lashing a clearance back past Forster before he could move, finally registering his first goal for the club in some style.
And quick as a flash, the Foxes were in front. Eric Dier stepped out of defence, and was caught out of position when Leicester won the ball back and countered with pace, leaving Maddison with a free shot to beat Forster and complete a quickfire turnaround.
Iheanacho adding a third, moments before the break, was the real sucker punch for Tottenham, with Dier standing off the Nigeria striker and allowing him time to pick out the bottom corner from just outside the area.
A resurgence of some kind was expected from Spurs after half-time but it never materialised. Instead Leicester thought they had a fourth when Barnes fired across Forster from a tight angle for a goal his performance had deserved - until VAR denied him on a narrow offside review.
He and Maddison had brought Leicester's attack to life but their new signings - Kristiansen, Tete and Harry Souttar - also impressed in a performance of real quality from the hosts.
And with time running out, Barnes did get his goal with an excellent placed finish into the bottom corner from 25 yards to put the shine on a superb win for Brendan Rodgers and his side.
Rodgers: You can see the difference January arrivals have made
Leicester manager Brendan Rodgers told Sky Sports:
"Without making excuses, there's a reason behind where we've been lacking and we weren't able to bring in players until January. We've been able to improve, and you see the difference it makes. The play, the set-up and the hunger that's there. You want to play fast, exciting football - and when we're playing well, we produce performances like that.
"It was an outstanding performance and win, a continuation from last weekend playing against a Champions League team with amazing quality.
"The players played with great bravery to press the game, be aggressive in the right moments, and tactically we were outstanding. With the ball we looked back to what we've been in previous times, dynamic, creative and a real threat to the goal. So overall, a very good performance.
"I've always said this group have character, and we responded to going behind magnificently to get ourselves back into the game."
Stellini: I'm sorry for lack of Spurs effort
Tottenham assistant head coach Cristian Stellini told Sky Sports:
"We didn't start badly, we started well and scored, but after that we probably thought it was a bit easier than normal. A game is never easy to play, and after that we have to apologise - the effort and our strength went down, and we have to continue to play with the same desire we had in the last game, and to be more consistent on that.
"Every goal you concede, there is something wrong - sometimes the mistake is one you can accept, sometimes less-so. It's about the whole team, not only one mistake or another. It's about the team, and the way the team has to play after a game we won against City, we have to forget this and continue to play with the same desire. This is the way.
"It happened last season too - we beat Man City, then we lost to Burnley. We have to be better in this aspect, if you beat Man City you have to continue in the next game. The next game is a Champions League game, we need to have the same confidence and be focused for 90 minutes. Not because you score and then lose the pace of the game.
"Antonio is fine, he's good, he's back - this is important, he has to take it easy a bit, because it's important to have him back soon, but we need him 100 per cent and not lose him again."
What's next?
Leicester play top-six opposition again next weekend when Manchester United play host on Sunday 19 February; kick-off 2pm, live on Sky Sports.
Tottenham are in Champions League action in midweek when travelling to play AC Milan in the first leg of their last-16 encounter on Tuesday 14 February - kick-off 8pm - before hosting West Ham in the Premier League next weekend on Sunday 19 February, kick-off 4.30pm, live on Sky Sports.