The Blues fell behind in the opening period – Tarik Muharemovic heading in for the visitors – and appeared in danger of suffering an early exit when Brenden Aaronson drove home a second immediately after the restart.

Yet our response to the adversity faced was emphatic. Two goals in two minutes from Cole Palmer, the first a penalty and the second a curled finish, brought us level, and Pedro Neto then put the Blues ahead with a well-taken strike.

Alonso's side didn't relent. Welbeck struck a fourth and, while Dominic Calvert-Lewin temporarily reduced the deficit, Valentin Barco's first Chelsea goal and a second from Welbeck ensured our progress at the expense of our old rivals.

Opportunities afforded

In his pre-match press conference, Alonso said those who hadn't played many minutes this season would be given a chance to make their mark. The Blues head coach was true to his word, as nine changes were made to the team that started at Arsenal.

Mike Penders started in goal behind a back three of Josh Acheampong, Maxence Lacroix and captain Levi Colwill. Malo Gusto and Pep Chavarria occupied the wing-back roles, 16-year-old Reggie Watson made his Chelsea debut in midfield alongside Barco, and Estevao Willian, Jamie Gittens and Danny Welbeck were in attack.

Given the unfamiliarity of the starting XI, the Blues unsurprisingly took some time to settle into the game. Our best effort in the opening exchanges came from Gittens, who worked goalkeeper Michael Zetterer with an effort from distance.

Falling behind

Leeds offered little threat until the 20-minute mark – then the visitors burst into life. Their first and second attempts on goal came in quick succession, and they brought out the best of Penders.

A long throw into the Blues penalty area caused panic and the ball sat up for Aaronson. He was denied at close range by a fine stop from our Belgian goalkeeper, who then reacted instinctively to push over Muharemovic's follow-up header.

However, it proved only a momentary reprieve as, after one corner was cleared behind, another Leeds delivery was met by Muharemovic at the back post, and he planted his header beyond Penders to put Leeds ahead.

Leeds had momentum and looked to strike again soon after the restart. Another attack into the Blues' half ended with the ball falling to Sean Longstaff, who fired over from 18 yards.

Our threat was limited during the remainder of the half. There were promising moments, such as an Estevao run that almost opened up a chance for Welbeck, an effort from Gittens deflected into the side netting, and a shot from Barco that bobbled wide, but it was a challenging half for Alonso's side.

Changes made

That perhaps informed the Spaniard's decision at the interval, as a quadruple substitution was made. Gusto, Watson, Estevao and Gittens were replaced. Reece James, Neto, Palmer and Rogers were introduced.

It got worse for the Blues before it got better, as Leeds grabbed a second goal two minutes after the restart. It was a well-worked strike, as a low cross into the box was delicately flicked on by Lukas Nmecha and Aaronson drove home his finish.

Two goals behind and facing an early cup exit, the Blues' resolve would be tested in the time that remained.

Roaring back

Our route back into the game started with a penalty. Dan James fouled the crossing Chavarria and referee Jarred Gillett pointed to the spot. Palmer stepped up and rasped a shot into the corner.

The noise inside Stamford Bridge increased. So did the tempo at which Alonso's side moved the ball. And two minutes after reducing the deficit, we levelled the contest. Palmer, again.

It was a simple enough goal, as Rogers steered a long throw into the path of the Blues' No.10, who expertly guided a 20-yard finish into the corner.

There was no let-up – and another attack soon followed. This time, Palmer was the provider as he guided a cross into the box for the onrushing James, whose clipped finish beat Zetterer but went the wrong side of the post.

No let-up

The turnaround was complete, though, on the hour mark. Palmer and Rogers were involved, as the former played a pass through to the latter, who on the slide guided the ball toward Neto. The Portuguese winger ran onto and measured his shot, which clipped the far post and nestled in the net.

Still, Alonso's side pushed for more. Palmer had a low drive blocked, but our fourth goal quickly arrived. Welbeck this time on the score sheet as he collected a low cross, shifted the ball onto his right foot, evaded two challenges and fired between the legs of Zetterer.

The Blues had breathing space – for ten minutes, at least. That was temporarily eroded when Calvert-Lewin drove home from inside the area and left Alonso's side facing a nervy finish.

Leeds sensed there was a path to parity and committed players forward. Important blocks and defensive interventions were made; Alonso's side had to work again.

Yet with ten minutes remaining, another powerful Rogers run and cross created our fifth. His delivery broke kindly to Barco, who slammed home his first Chelsea goal

With that, our progress was sealed, although the scoring wasn't over. In the fourth of six added minutes, another attack ended with Barco skewing a shot toward goal, which Welbeck redirected into the corner to round off the evening.

What comes next...

The Blues are back at Stamford Bridge on Saturday afternoon, as we take on Hull City in Premier League action. Kick-off is at 3pm (BST), and you can follow all the action on the Chelsea Official App and website.

The teams

Chelsea: Penders; Acheampong, Lacroix, Colwill (c) (Fofana 76); Gusto (Neto 46), Watson (James 46), Barco, Chavarria; Estevao (Palmer 46), Welbeck, Gittens (Rogers 46)
Chelsea substitutes: Martinez, Hato, Quenda, Joao Pedro
Goalscorers: Palmer 53 pen, 55, Neto 60, Welbeck 65, 90+4, Barco 80
Booked: Watson 45+1

Leeds United: Zetterer; Justin, Bijol, Muharemovic; James, Ampadu, Longstaff, Bard; Wilson, Nmecha, Aaronson
Leeds United substitutes: Trafford, Bogle, Gudmundsson, Elvedi, Tanaka, Stach, Okafor, Bahoya, Calvert-Lewin
Goalscorers: Muharemovic 23, Aaronson 48, Calvert-Lewin 75

Attendance: 35,696
Referee: Jarred Gillett