Southampton lead after a slightly odd half of football.
Chelsea dominated throughout yet barely created anything, and they were punished for the sterility of their domination when Takumi Minamino scored a delicious goal in the 33rd minute.
McCarthy; Salisu, Bednarek, Vestergaard, Bertrand; Djenepo, Ward-Prowse, Romeu, Minamino; Ings, Redmond
Subs: Stephens, Adams, Tella, Ramsay, N’Lundulu, Forster, Ferry, Jankewitz, Chauke
Mendy; Azpilicueta, Rudiger, Zouma; James, Kovacic, Kante, Alonso; Mount, Abraham; Werner
Subs: Kepa, Christensen, Emerson, Chilwell, Gilmour, Jorginho, Hudson-Odoi, Ziyech, Giroud