Never underestimate Chelsea’s capacity for chaos. Only they could go 2-0 up against Championship opposition in an FA Cup quarter-final and end up needing a stoppage-time winner to go through after a second half that will be remembered for Axel Disasi’s preposterous own goal, more venom from the crowd and Cole Palmer lifting Stamford Bridge’s toxic atmosphere with a superb assist for Carney Chukwuemeka.

Still so short of leadership and experience when the pressure rises, Chelsea had flirted with humiliation before Palmer’s calm and ingenuity set up Chukwuemeka for 3-2 in the second of two added minutes. The collapse was astonishing, Disasi sparking it when he gave ­Leicester hope with one of the all-time ­bloopers. Chelsea, their composure eradicated by the centre-back’s ­aberration, were in the midst of a meltdown when Stephy Mavididi hauled Leicester level.

Emotions ran high. The home fans tore into Raheem Sterling, who missed a penalty and spurned a glorious opportunity during the first half when he blasted a free-kick over moments after Leicester had lost Callum Doyle to a red card with 17 minutes remaining. They hammered ­Mauricio Pochettino with chants of “You don’t know what you’re doing” when Chelsea’s head coach brought Chukwuemeka on for Mykhailo Mudryk instead of Sterling.

It was a reminder that stability continues to elude Pochettino’s young side. They lurch between extremes, their football dazzling at times, their decision making too often ­bewildering. At the end, though, goals from Chukwuemeka and Noni Madueke meant Chelsea were through to their second semi‑final of the season, this time against Manchester City at Wembley.

Pochettino could still end this rollercoaster campaign on a high, but Leicester did not make it easy. Enzo Maresca’s men have wobbled of late, their lead at the top of the Champion­ship whittled away after one win in five games, but they refused to be overawed.

Chelsea had to be on their game to make the most of hosting second‑tier opposition for the third time in the competition this year. Leicester caused problems during the first half. Patson Daka and Wout Faes headed wide from inviting positions, the ­latter after the suspect Robert Sánchez came off his line and failed to claim a corner.

For all Leicester’s bravery, though, many of their players were below the required standard in the top flight. Harry Winks, who played well alongside Kiernan Dewsbury-Hall in ­midfield, has dipped since starting for ­Pochettino’s Tottenham in the Champions League final five years ago.

Ultimately, Leicester are ­hovering between two eras, the impact of rele­gation still present, a points ­deduction for breaching profit and sustaina­bility regulations looming if they do go up. Wilfried Ndidi, the Nigeria midfielder, was the only player in either starting lineup who played when Leicester beat Chelsea in the 2021 final. A centre-back ­pairing of Faes and Jannik Vestergaard did not inspire confidence.

Chelsea fancied their chances. Pochettino reacted to Enzo ­Fernández’s suspension in midfield by using a 4-2-3-1 system. Mudryk started on the left, ­Sterling went through the middle, and ­Chelsea were soon leading.

The goal was sparked by Moisés Caicedo’s tackle on Abdul Fatawu. The ball went to Palmer, who released Nicolas Jackson. Faced by Vestergaard, the striker surged clear and presented the left-back, Marc Cucurella, with a tap-in for his first goal for Chelsea.

More goals should have followed. There was a weird moment when Fatawu conceded a penalty with a lunge on Sterling. Palmer has converted five spot-kicks this season, so it was a surprise to see Sterling grab the ball. His kick was too central and Jakub Stolarczyk kept the score at 1-0.

Sterling then went through and chipped wide from Caicedo’s pass. Nobody can ever accuse him of ­hiding, though. He had an assist when he drove down the left and set up Palmer just before half-time.

It was too simple. Chelsea prefer it bewildering. Six minutes into the ­second half, Disasi obliged. ­Racing back to deal with a loose ball on the right, the defender felt some ­pressure from Daka and panicked, even though he was 40 yards from goal. Sánchez, equally ­unconvincing in possession, was too far to his left and the goalkeeper was powerless to prevent Disasi’s slice spinning into the net.

Chelsea’s structure disappeared. It came as no surprise when Mavididi beat Malo Gusto and bent a magnificent shot beyond Sánchez. Leicester were emboldened to chase a third. Chelsea countered through Jackson. Doyle cynically brought him down on the edge of the area. Andrew ­Madley, the referee, pointed to the spot, awarded a free-kick after checking a replay, and sent Doyle off.

The mood turned weird. Abuse rained down on Pochettino and ­Sterling. Leicester’s 10 men dug deep. There were boos when Sterling made way for Madueke.

Time was on Chelsea’s side. ­Chukwuemeka combined with Palmer, whose backheel sent the midfielder through to score. The tension lifted, Madueke’s deflected shot flew in from 20 yards. It remained hard to forget about the earlier discord.