And just as against Villa, we were grateful to Kepa who got the faintest touch on Theo Walcott’s penalty to tip it onto the post. Although Mason Mount then saw his spot-kick superbly saved by Fraser Forster, Saints sub Will Smallbone blazed over and James was on hand to complete the job once more.

In the initial 90 minutes Kai Havertz had given the Blues the lead on the stroke of half-time with a powerful header, but our lead evaporated almost as soon as play restarted courtesy of a close-range Che Adams goal.

Chances were traded at both ends, with Kepa and Forster in fine form to keep the score at 1-1 and send the tie to a shoot-out. Two injury-time saves from our Spaniard stand out, and a further stop from Walcott would prove decisive when the teams went toe to toe 12 yards out.

We will find out our quarter-final opponents on Saturday morning, and you can watch the highlights and full game of this one shortly, at 1am UK time tomorrow (Wednesday).

The selection

There were six fresh faces in the Chelsea side, with Thomas Tuchel’s selection resembling that of the previous round’s victory over Aston Villa.

Kepa was in goal, and Malang Sarr returned to the back three alongside James and Trevoh Chalobah. Captain Marcos Alonso came in at left wing-back for his first start in a month, and there was a place in midfield for Saul. Further forward, Ross Barkley started his first game for Chelsea since September 2020 on the left side of the front three when we had possession. Hakim Ziyech was the other forward supporting Havertz in attack.

Harvey Vale, 18, was named among the substitutes for the first time, as was goalkeeper Teddy Sharman-Lowe.

Save from Saul

The Blues probed with good intent in the early stages. From the first corner we won, Barkley delivered and an unmarked Saul headed towards the top corner, only to be denied by a fingertip Forster save.

With two much-changed teams the tie had an enjoyably open feel to it from the get-go. There was no shortage of green grass in behind the Saints’ backline for us to try and exploit, but initial attempts to do so went unrewarded.

On 15 minutes, Havertz drove inside off the left flank and thumped a 20-yarder past the post with Forster at full stretch, and that was the closest either team would come until Havertz stung Forster’s palms 10 minutes later. Barkley and Alonso had been instrumental in the build-up, with the German proving a real nuisance in the central striking role.

Balancing out

It wasn’t until the half-hour that the Saints truly threatened our goal. Adams flicked a corner on at the near post and it reached fellow forward Adam Armstrong at the far stick, but under pressure from Alonso he couldn’t guide his header on target.

Kepa was then called upon to make his first stop of the night after a loose ball ran Stuart Armstrong’s way inside the box. Chalobah had taken the sting out of the ensuing strike to aid his keeper’s cause.

Breakthrough on the brink of HT

As the interval approached, fluency in possession remained elusive for Tuchel’s side until a glorious 50-yard ball from Saul released Alonso, whose cross was put behind for a corner. Ziyech centred and there was Havertz, from a standing jump, to accurately plant his header in the bottom right-hand corner.

If our end to the first half couldn’t have gone any better, the start to the second couldn’t have been worse. Barely 90 seconds in, Kyle Walkers-Peters burst into the box and drilled a shot goalwards that squeezed through Kepa before Adams knocked it in.

Havertz almost immediately restored our advantage, drawing Forster into a good stop with his feet after Callum Hudson-Odoi had exploited space down our right. The German’s touch then eluded him when put through on goal. Down the other end, Kepa had to be alert to parry Adam Armstrong’s shot to safety.

The frenetic pace continued unabated. Barkley was twice denied by Forster at close quarters, either side of a James free-kick being tipped over by the Saints stopper and him holding a Saul header.

Subs and position switch

Midway through the second period, both managers made a double change. For us, Mount and Ben Chilwell came on for Ziyech and Barkley. Chilwell went to right wing-back, and Hudson-Odoi moved to the left side of the front three, with Mount on the opposite flank.

In the 74th minute, Saul curled a shot wide from the edge of the box following good build-up play from Hudson-Odoi and Havertz, and the Spaniard was thwarted by Forster for the third time tonight with a more accurate effort from range as the Matthew Harding Stand urged him to shoot.

Within seconds of his introduction off the bench, Southampton youngster Smallbone found himself free in the box only to see Kepa claw his header away.

The final 10 minutes produced plenty of endeavour, in keeping with the rest of the contest, but no winning goal. Hudson-Odoi hit the side-netting with our best attempt, while Kepa produced two fantastic stoppage-time saves from consecutive corners to keep out Lyanco Vojnovic and then Mohammed Salisu. It took the tie to penalties.

Spot-kicks settle it

As in the third round, the spot-kicks took place in front of the Matthew Harding Stand, with the visitors again going first. Armstrong and Alonso scored with ease before Kepa tipped Walcott’s strike onto the right-hand post. Forster did even better to somehow palm Mount’s fierce shot over the bar. The next two penalties were scored but when Smallbone leaned back and whacked his shot into row Z, Chilwell – who had hit the bar against Villa – and James made no mistake to send us through.

Southampton’s Adam Armstrong went first – scored high – 0-1Alonso took Chelsea’s first – scored bottom right – 1-1Walcott – hit post via a tiny Kepa touch – 1-1Mount – saved brilliantly by Forster – 1-1Long – scored bottom left – 1-2Hudson-Odoi – scored coolly – 2-2Smallbone – skied over the bar – 2-2Chilwell – scored in the corner – 3-2Romeu – down the middle – 3-3James – sent Forster the wrong way! – 4-3

What’s next?

The longest domestic away game of the season is on Saturday as we travel to Newcastle. A week tonight we are at Malmo in the Champions League with the fixtures continuing to come thick and fast.

Chelsea (3-4-3): Kepa; James, Chalobah, Sarr; Hudson-Odoi, Kovacic, Saul, Alonso (c); Ziyech (Mount 67), Havertz, Barkley (Chilwell 67)Unused subs Bettinelli, Sharman-Lowe, Rudiger, Thiago Silva, Jorginho, Vale.Scorer Havertz 44

Southampton (3-4-3): Forster; Valery, Lyanco, Salisu; Walker-Peters, S.Armstrong (c) (Smallbone 77), Diallo (Romeu 77), Djenepo (Livramento 83); Tella (Walcott 67), Adams (Long 66), A.ArmstrongUnused subs Lewis, Bednarek, Perraud, Redmond.Booked Diallo 23, Djenepo 80, Forster 90+1Scorer Adams 47

Referee Kevin FriendCrowd 39,766