Former England captain Alan Shearer admits he doesn't understand the tactics of Chelsea boss Graham Potter.
James Ward-Prowse scored the only goal of the game from a free-kick, to lift the spirits of a rudderless Southampton - and put more pressure onto Potter's role as manager at Stamford Bridge.
Speaking to Match of the Day, ex-Premier League legend Shearer could not understand what the former Brighton gaffer was trying to do with Chelsea's frontline.
"It was a mixture of magnificent defending and goalkeeping and really poor forward play from Chelsea," Shearer said.
He highlighted issues among Chelsea's dazzling array of forward talent on show, including David Fofana, Kai Havertz, Raheem Sterling, Joao Felix and Conor Gallagher among others.
Shearer said: "At times, I'm lost to see what they're trying to do. The first half they had Fofana up there, they took him off, brought Sterling on, because they didn't create anything.
"This is what I mean when I say I struggle when I look at Chelsea. Ok Havertz there, Felix there, they brought Sterling on, who was probably their best player in the second half.
"But Sterling's got the ball there, there's no options, so he goes back, he goes square, that allows Southampton to get men behind the ball and make it very difficult for them."
As well as Sterling's movement back, Gallagher was also highlighted for his play, which allowed the Saints to get behind the ball. Shearer said: "When he doesn't get his shot away, that allows Southampton to get players behind and defend."
Shearer summed up Chelsea's issues up front by ruminating on "the lack of options. The lack of a centre forward, that killer instinct".
He also spoke about Potter's future, which is under intense scrutiny following a run of poor results, including just one win in the calendar year so far.
"It's a worrying time for him, he's under huge pressure," Shearer fumed. "One win in ten, four goals in the last ten games in all competitions. Nowhere near good enough in the forward position. Miles away from it."