Southampton manager Ronald Koeman expects Charlie Austin to miss up to four weeks with the hamstring injury he sustained against AFC Bournemouth.
Austin limped off an hour into Tuesday's 2-0 defeat at the Vitality Stadium with strike partner Shane Long forced off 10 minutes later.
Koeman said after the match that he expected January signing Austin to miss a number of weeks and confirmed on Thursday that his absence could last a month.
Long will miss Saturday's visit of Sunderland in the Premier League due to a knee problem.
"We did a scan yesterday and [Austin] will be out for three to four weeks with a hamstring," Koeman explained.
"Shane Long will not be available for the weekend [against Sunderland] but it's a different type of injury and we have good hope he will be available next weekend.
"It was a knock on his knee and it's painful but it won't be a problem for next weekend."
Austin has suffered hamstring problems in the past and was accused by West Ham co-chairman David Sullivan of being prone to knee injuries when the club were reported to be interested in signing him from QPR.
But Koeman added: "[The injury is in] a different place, it's not the same injury he had when he came to Southampton.
"It's a grade one hamstring injury and normally that's between two and four weeks but it wasn't the worst injury.
"It's part of football, it's hard to take for Charlie and it's hard for us because we lost two front players in 10 minutes.
"Now we need other strikers to do the job."