In what was a pulsating affair at Stamford Bridge, many of Thomas Tuchel’s rotational options failed to make their case for the starting XI on a weekly basis.
Indeed, only Kai Havertz (who scored their goal with a header on the stroke of half-time), Kepa Arrizabalaga and Trevoh Chalobah (who has emerged as a genuine first-team option anyway) looked impressive, although a case could be made for Callum Hudson-Odoi.
Che Adams leveled three minutes into the second-half and it was largely the away side who had the better of it towards the end in SW6, with Kepa pulling off two stunning saves in the final minute to keep his side in it.
Reece James scored the winning spot-kick after teammate Mason Mount had missed.
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Dan Kilpatrick’s full-time verdict
Having beaten Aston Villa here on penalties after a 1-1 draw in the third-round, Chelsea repeated the trick tonight. It’s fair to say Tuchel’s fringe players, notably Barkley, Ziyech and Saul, did not do enough to convince him they deserve more minutes in the League but Havertz’s confidence seems to be returning, which is a timely boost.
Reece James scores! Chelsea have won it 4-3.
Oriol Romeu scores! 3 -3.
Chilwell scores, 3-2 Chelsea.
Will Smallbone misses! 2-2.
Shane Long scores! 2-1 Southampton
Mason Mount misses Chelsea’s second spot-kick!
The Saints fans will love that.
Alonso scores for Chelsea.