West Ham's injury problems continue to mount after Arthur Masuaku was ruled out for at least six weeks with ankle ligament damage.
The Hammers acted swiftly to draft in Masuaku from Olympiacos in August after first-choice left-back Aaron Cresswell sustained a knee injury.
Masuaku has started six games in all competitions this season but the 22-year-old is now set to miss a chunk of the campaign after injuring his ankle during Wednesday's EFL Cup win over Accrington Stanley.
"Arthur Masuaku has damaged his ligaments and we will know better in one week when he will be back, but it will at least six weeks," West Ham boss Slaven Bilic told a media conference on Friday.
"It is not good news and both our left backs have damaged their ligaments, but we still have a good team."
Masuaku joins Winston Reid (knock), Andy Carroll (knee), Andre Ayew (thigh), Cresswell and Diafra Sakho (back) on the sidelines.
However, Reid is nearing a comeback and Bilic also expects Carroll and Cresswell to return after the next round of international fixtures.
"Winston Reid is back in training and Alvaro Arbeloa has joined the team," the Hammers boss added. "The injuries are not ideal but we will still have a good team.
"I saw reports that Andy Carroll had a setback but that is totally false. We are expecting him and Aaron Cresswell back after the break."
West Ham have not made the start many expected after finishing seventh last term and investing heavily during the close-season.
The Hammers have won just once in the Premier League and lost their other four league games, but Bilic hopes this weekend's clash with Southampton at London Stadium will prove the turning point as it did last season following a 2-1 win in late December.
"This is a great opportunity for us to get out of the trouble we are in," he said. "It will bring back confidence and the belief if we can get the victories.
"The reaction has been there in training and we always train hard. We have to do that in games and for ninety minutes.
"Southampton got a good victory in Europe last week and it will be another hard game for us. I am expecting us to be really good on Sunday.
"We had a similar position when we played Southampton last season. We had gone a few games without a win but we got the players back and confidence back and we started winning again."