Adam Lallana will miss the start of Liverpool's Premier League campaign after being ruled out for a 'significant period of time' with a thigh problem.
The midfielder suffered the injury in Wednesday's Audi Cup final penalty shoot-out defeat to Atletico Madrid, during which he was substituted at half-time.
Pool boss Jurgen Klopp said Lallana was likely to miss "a couple of months, not weeks", ruling him out of the club's two-legged Champions League play-off with Hoffenheim.
"This is not news we would have wanted," Klopp said.
"Unfortunately, the damage is such that it will likely mean Adam is out for a couple of months, not weeks, so I think we can rule him out of August and September.
"Beyond that, we will monitor and wait and see.
"He is a boy with a world-class attitude to everything professionally and he has always come back in good time from injury setbacks."
Lallana's absence comes less than a week after Liverpool ended their interest in signing RB Leipzig midfielder Naby Keita, who would have competed with Lallana for a starting place.
The loss of the 29-year-old leaves Klopp somewhat light in central midfield, with Jordan Henderson, Emre Can and Georginio Wijnaldum as recognised options in the position.
Philippe Coutinho was successfully deployed in the middle of the park at the tail end of last season and has returned to the role in recent friendlies but is used to operating in a more advanced role.
Klopp, meanwhile, has welcomed a Champions League clash with Hoffenheim, admitting he felt that he would be heading back to his native Germany in the play-off round.
Klopp hailed the tie "really exciting" after Liverpool and Hoffenheim - who both finished fourth in their respective leagues last season - were paired together at yesterday's draw in Nyon.
Liverpool will head to Klopp's homeland for the opening leg on August 15 before hosting Hoffenheim at Anfield eight days later.
"Very interesting. It was exactly what I expected - if there's a choice we always seem to take the German team!" Klopp said.
"It's not an easy game. I'm completely fine with it, I'm happy to know and now we can start preparing. First we'll play Watford but at the same time we'll start preparing for Hoffenheim and it's really exciting."
The tie pitches Roberto Firmino against his former club as the Brazilian striker spent four seasons at Hoffenheim before joining Liverpool in 2015.
Klopp has a mixed record versus Hoffenheim - winning five, drawing six and losing five of the 16 games with them while he was in charge of Mainz and Borussia Dortmund - but Liverpool have fared well, progressing from 14 of 16 two-legged knockout ties against German opposition.
The 10 winners from the Champions League play-off stage will join the 22 teams who have already qualified for the group stage.
Everton host Croatia's Hajduk Split in the Europa League play-off first leg on August 17 with the return on August 24.