The Spain international will now face a spell on the sidelines but the club are hoping the problem is not serious and he could return to action within weeks.
The 31-year-old was forced off early in the second half of the Reds’ opening Premier League match of the new season at Fulham last Saturday.
No timeframe has yet been put on his return and he will undergo another scan later this week to determine the extent of the problem.
Liverpool host Crystal Palace in their second Premier League game next Monday before travelling to Manchester United the following week.
The Reds drew 2-2 at Craven Cottage in their opener after twice coming from behind.