Andy Robertson’s return to Liverpool training has been delayed after the left-back picked up a hand infection.
The Reds confirmed the 25-year-old has undergone minor surgery but should still travel to the United States with the rest of the squad next week.
Jurgen Klopp is already without a cluster of first-team players, with Sadio Mane, Mohamed Salah and Virgil van Dijk returning later due to international duty.
Robertson played a crucial role in the Champions League-winning campaign and his understudy, Alberto Moreno, recently left the club on a free transfer.
Liverpool are yet to sign a replacement, with 17-year-old defender Sepp van den Berg their only signing thus far.
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Following the Reds opening pre-season friendly, a 6-0 victory over Tranmere Rovers on Thursday, Klopp hinted at a quiet transfer window for the club.
He said: “The transfer market is open, I don’t know exactly until when [August 8]. “The whole of Europe had the wonderful idea to close the transfer window early and the only country that did it was England! We close it three weeks before all the others.
“So yeah, we will see what we do, I don’t think it will be the biggest transfer window of all time.”
Liverpool face Bradford City on Sunday before heading to the US for friendlies against Borussia Dortmund, Sporting Lisbon, Napoli and Sevilla.