Thomas Tuchel was pleased Chelsea were able to overcome some last-minute changes to team selection to edge past Southampton following another penalty shoot-out in the Carabao Cup.
The Blues required spot-kicks to see off Aston Villa in the previous round at Stamford Bridge and it was the case again in the last-16 after Che Adams' tap-in cancelled out Kai Havertz's 44th-minute opener.
Both sides had chances to grab a second but penalties were required and although Mason Mount was denied from 12 yards by Fraser Forster, Theo Walcott and Will Smallbone fired off target for Saints to ensure Chelsea progressed by a 4-3 score.