The Spaniard was substituted after pulling up during Sunday's 3-0 victory over QPR, and Reds assistant boss Colin Pascoe has now confirmed the severity of the blow
The Spaniard was substituted after pulling up 71 minutes into the game at Loftus Road, which the Merseyside club won thanks to Daniel Agger's header and a Luis Suarez double.
And Pascoe, who led the team in the absence of the ill Brendan Rodgers, has now conceded that Liverpool may be without the full-back for some time.
"Unfortunately it looks like he's got a tear in his hamstring," he told reporters.
"He was terrific today, absolutely superb, and the way he's been performing these last couple of months has been a joy to watch.
"It's a shame, and hopefully he's not out for too long."
The 26-year-old has appeared in 12 Premier Leagues so far this season.