Southampton make two changes from the team that lost to Wolves last weekend: Mohammed Salisu and Moussa Djenepo replace the injured pair of Kyle Walker-Peters and Stuart Armstrong. Salisu is starting a Premier League game for the first time, and it looks like Ralph Hasenhuttl may have switched to a back three.
There are four changes for Chelsea. Edouard Mendy, Kurt Zouma, Reece James and N’Golo Kante return to the side, with Kepa Arrizabalaga, Andreas Christensen, Callum Hudson-Odoi and Jorginho dropping to the bench.
Southampton (possible 3-4-2-1) McCarthy; Bednarek, Salisu, Vestergaard; Djenepo, Ward-Prowse, Romeu, Bertrand; Minamino, Redmond; Ings.
Substitutes: Forster, Stephens, Ramsay, Ferry, Tella, Jankewitz, Chauke, Adams, N’Lundulu.
Chelsea (3-4-2-1) Mendy; Azpilicueta, Zouma, Rudiger; James, Kante, Kovacic, Alonso; Mount, Werner; Abraham.
Substitutes: Arrizabalaga, Christensen, Chilwell, Emerson, Jorginho, Ziyech, Gilmour, Giroud, Hudson-Odoi.
Referee Anthony Taylor.