Liverpool face potential defensive problems ahead of their Premier League opener against West Ham United on Sunday with Virgil van Dijk and Joe Gomez the only senior centre-backs fit and available, manager Jurgen Klopp said.
Joel Matip (hip) and Ragnar Klavan (hamstring) both missed the 5-0 friendly win over Napoli because of injuries and are doubtful for Liverpool's final preseason game against Torino on Tuesday.
"Joel, we'll have to see," Klopp said, according to the Liverpool Echo. "Klavan, shouldn't be too serious, but if Tuesday is too early, I don't know yet.
"Maybe we will do some magic things with the formation on Tuesday. I don't know how we will do it."
Croatia international Dejan Lovren will rejoin the squad on Monday after an extended break following the World Cup but is a doubt for the next two games.
"Dejan didn't train so far," Klopp said. "He probably won't play Tuesday and Sunday will be very difficult as well. The first two league games at least are in the preseason [for World Cup players]."
Liverpool finished fourth last season and reached the final of the Champions League, where they were beaten by Real Madrid.
"The league will be difficult," Klopp said. "It is not about judging our situation and thinking 'Wow, really good.' We need to be ready each week -- not only for a few games. That is our challenge."