These early rounds of the Carabao Cup have become a test of depth and desire for the heavyweights of the Premier League.

Seldom are the big beasts rattled by those from the EFL anymore but there’s always a good chance they will get a fright if the fringe players show up and think they can go through the motions like it is some sort of charity match.

That’s the way it went last night for Xabi Alonso. His Chelsea team were outfought, outplayed and two goals down before a second-half cavalry charge from the A-listers on the bench, triggered by a soft penalty awarded by Jarred Gillet for an embarrassing overreaction by Pep Chavarria to minimal contact from Dan James.

Cole Palmer rolled it in, cool as a you like. Two minutes later, Palmer scored again, a sublime finish curled low into the bottom corner with a swish of his left boot from the edge of the penalty area to peg the tie level at 2-2.

Home fans, numbed into silence by the first half, were supercharged and Leeds caved in. 'A crazy, nuts game,' said Leeds boss Daniel Farke. 'We played with confidence, not even a chance for them, then the referee decided to give a penalty. No-one in the stadium was asking for it.

'All of a sudden, quality players and the momentum was on their side. One small situation can change the whole momentum of the game.'

Pedro Neto produced a copy of Palmer’s second to nudge Chelsea ahead and when Danny Welbeck added the fourth it completed a burst of four goals in 12 sizzling minutes. Three of them were set up by Morgan Rogers.

Wobbles at the back will nag at Alonso. Dominic Calvert-Lewin pulled Leeds back to within a goal once again at 4-3 and Chelsea have conceded a total of 10 in the first five games of the season. At the other end they have scored 16.

Hull City, who have score four and conceded two in the same number of games, are the next visitors. It should be intriguing.

Valentin Barco averted an anxious finale with the fifth, a fourth goal created by Rogers, who pointed out his impact as Palmer collected the man of the match award. 'I had four assists and he scored a penalty,' said Rogers.

And Welbeck’s second, deflecting a mishit Barco shot past hapless Leeds goalkeeper Michael Zetterer in added time, booked Chelsea into the fourth round but the tie with an emphatic result albeit it certainly not a six-goal stroll.

Nine Chelsea changes included a debut for 16-year-old midfielder Reggie Watson, who signed from Crystal Palace two years ago. Watson, son of Wigan FA Cup goal hero Ben, became the club’s fourth youngest player of all time.

'We have all been Reggie Watson one day, hopefully he will enjoy it,' said Blues boss Alonso before kick-off. Although, there was little for the home team to enjoy as Leeds came out at a fierce tempo. They snapped into tackles, bristled with the competitive edge missing from a young and lightweight Chelsea and threatened at set pieces including Ethan Ampadu’s long throw.

Leeds deserved their lead, scored from a corner after a fine double save by Chelsea Mike Penders, from Brenden Aaronson and Tarik Muharemovic. Harry Wilson swung the corner deep and Muharemovic climbed at the far to head in his first Leeds goal.

The Bosnia international signed for £34million from Sassuolo in Italy was best known before moving to Leeds for being on the receiving end of Folarin Balogun’s lunge which led to a red card for the USA striker and the great diplomatic skirmish of the World Cup summer.

Leeds would regret not having more than one goal to show for their first-half dominance. Alonso moved ruthlessly to make four changes at the interval.

On came Palmer, Rogers, Neto and Reece James but his team quickly conceded again. Barco was easily dispossessed on the break and punished by Ampadu, whose low cross was swept in by Aaronson.

'I need to take the blame,' said the Chelsea boss in defence of his young players. 'When you don’t have time to work it’s difficult to compete at this level. I will have a deeper assessment about how to help my players have a bigger impact. Maybe I made it too difficult against a strong side. But you need to react and make decisions.'