Roberto Firmino injury latest in Jurgen Klopp's pre West Ham v Liverpool press conference
Firmino limped off 12 minutes from time during Liverpool's 2-0 Champions League win at home to Atletico Madrid on Wednesday having only been introduced at half-time from the bench.
Scans have ascertained the extent of the hamstring problem, with the striker out for the foreseeable future and having withdrawn from Brazil's squad for their forthcoming World Cup qualifiers.
Roberto Firmino is facing at least a month on the sidelines after Jurgen Klopp confirmed the striker's hamstring injury is a serious one.
It is the second hamstring issue the Brazilian has suffered this season having missed almost a month after being injured at home to Chelsea in August.
Klopp said: "Bobby is not good news with a serious hamstring injury, really unfortunate.
"We don't know exactly how long he will be out but it will be not now after the international break directly. We have to work on that.
"Losing Bobby Firmino is a blow. We have known for two days it was serious.
"We are talking weeks, still. More than four. I'd consider that a serious injury. Then we have to see. Bobby is a quick healer."