Blues will learn their fourth-round opponents next week.

Chelsea struck four times in a blistering 12-minute spell in the second half as Leeds United suffered a dramatic Carabao Cup collapse, going down 6-3 in the third round at Stamford Bridge.

The visitors were 2-0 ahead shortly after the restart through Tarik Muharemovic and Brenden Aaronson against a Chelsea side that showed nine changes from Sunday’s defeat to Arsenal, but everything altered after Xabi Alonso introduced Cole Palmer as part of four half-time substitutions.

Palmer scored twice in the space of two minutes to level the match — the first from the penalty spot — before another interval substitute, Pedro Neto, completed a six-minute turnaround.

Danny Welbeck made it four, while Morgan Rogers underlined his influence from the bench by providing three assists.

Dominic Calvert-Lewin got on the scoresheet as Leeds tried to recover from what had been an impressive away display, but the evening was sealed as a nightmare when Valentin Barco netted his first goal for the club to make it five. Welbeck then headed home a sixth in stoppage time.

The wildly swinging contest offered further proof of Chelsea’s new reality under Alonso: a strong first XI capable of dazzling attacking football, but also a squad short on depth and vulnerable at the back.

Double bubble: Danny Welbeck

Chelsea’s second-string side were comfortably second best in the first half. Reserve goalkeeper Mike Penders produced two fine saves, but then made an expensive mistake that gifted Leeds their opener, conceding an unnecessary corner from which Muharemovic headed in.

There was hardly any reaction from the Blues. Their only opportunity came when Reggie Watson — the 16-year-old debutant son of former Wigan defender Ben — began the move with an excellent pass out wide, which Pep Chavarria flicked into the path of Jamie Gittens, whose effort was pushed into the side-netting by goalkeeper Michael Zetterer.

Alonso had clearly seen enough. He sent on Reece James along with Rogers, Neto and Palmer for the second half, but Chelsea’s position worsened almost immediately.

A little over two minutes after the restart, Barco gave the ball away needlessly and Leeds worked it out to Ethan Ampadu, who delivered a cross. Lukas Nmecha applied a clever flick and Aaronson arrived unmarked to smash home.

What followed was a remarkable comeback, driven by Rogers and Palmer. Dan James stood on Chavarria’s foot and Palmer converted from the spot to make it 2-1.

His equaliser moments later was neatly finished, though Zetterer will feel he should have done better, as the ball was gently guided into the corner while the goalkeeper was left strangely rooted to the spot.

Neto put Chelsea in front from a Rogers pass before the hour mark as Leeds’ collapse gathered pace.

Welbeck’s strike was arguably the pick of the goals. Rogers found him with a low pass into the box, but the experienced forward still had plenty to do, dragging the ball inside, skipping past his defender and firing directly through Zetterer.

Calvert-Lewin finished smartly from Noah Okafor’s cross as Leeds briefly found fresh hope, but that was quickly snuffed out when Barco drilled in a fifth, before Welbeck headed in his third Blues goal.