Cesar Azpilicueta:
Prior to the match, with both teams waiting to march onto the field, Azpilicueta was mocked by a young Southampton mascot. It was a light moment that broke the tension pre-match, and it also proved to be the only bit of fun on the day for the Spanish defender.
Azpilicueta looked his age in this one. The 33-year-old defender struggled on the right-hand side, where he started in place of Reece James, who was out sick.
He conceded the corner that led to Southampton's first goal, and then mis-hit his clearance right to Lavia for the youngster's fine finish. In general, Azpilicueta struggled with the pace of the game as James' presence was sorely missed.
The England star is irreplaceable these days as questions remain about Azpilicueta's ability to truly back him up as a pure right-back.
Jorginho/Loftus-Cheek pairing:
For years, Tuchel's preferred formation has included three centre-backs, and nights like this show why.
Chelsea simply don't have the personnel to play in a four-at-the-back system right now, as the midfield left the backline exposed too often.
Jorginho struggled defensively and cannot play as a pure No. 6 without some sort of cover. Loftus-Cheek had a promising start, but was then far too predictable on the ball after the first few minutes, proving a detriment as the game wore on. And Mount did well enough, but obviously doesn't offer as much of a defensive presence.
Do Chelsea need a stronger presence like Declan Rice? Quite possibly. Would a healthy N'Golo Kante mask these sorts of problems? Maybe. Are they better suited for a three-at-the-back system? Most definitely.
It was a night to forget for the Blues' midfield.
Christian Pulisic:
The American was benched for the fifth consecutive game as transfer rumors continue to swirl.
Recent reports say that Pulisic will not leave Stamford Bridge, despite links to a loan move to Manchester United. He will instead be asked to fight for his place with Tuchel unwilling to let him go.
All of that, then, for him to just be thrown into the game out of position after the team's initial setup didn't work.
Pulisic is not a wing-back, and while it is nice for him to get onto the field, minutes in that part of the pitch don't help anyone. After coming on in the second half, Pulisic struggled, turning the ball over twice early and never really making much of an impact from where he was on the field.
It doesn't look like he'll leave, and that will likely be frustrating for a player who can't seem to ever get onto the field in his preferred position.