Ricardo Pereira faces six months on the sidelines and boss Brendan Rodgers admits the full-back "will be a big miss".
The Portugal defender ruptured his Achilles in the final pre-season friendly against Sevilla last weekend and Rodgers confirmed the extent of his injury with the new season due to kick off on Sunday.
"He was looking so good and this is a massive blow to him," Rodgers said. "It is such a shame because a lot of our game idea over the summer was based around full-backs and him in particular."
Rodgers is at least relatively well-stocked at the position, with James Justin, Timothy Castagne and Luke Thomas all able to fill in for Pereira.
"He had his operation last night and he'll recover now, get strong again and come back better I'm sure," said Rodgers.
"He’ll be a big miss for us but we have to push on."