Barcelona defender Thomas Vermaelen is set to undergo a number of tests on Monday to discover the extent of the injury he suffered during the 5-0 away win over Real Betis on Sunday evening.
Vermaelen sustained a hamstring problem in his left leg in the first half and was replaced by the returning Samuel Umtiti a few moments before the interval.
As yet, a time-frame on the Belgian's recovery remains unknown, but the picture is likely to become clearer once the tests are done and the damage is properly assessed.
It comes as a huge blow to 32-year-old Vermaelen, who was enjoying a real run of games for the first time in his Barça career after being ravaged by persistent injuries.
Filling in for the injured Umtiti, Vermaelen had started the last six La Liga games for the Catalans, including the one against Betis. He also appeared in three Copa del Rey fixtures during that time, starting two of them, and was finally beginning to justify his place at the club.
But with Umtiti fit and back alongside Gerard Pique, combined with the recent arrival of Colombian international Yerry Mina from Palmeiras, Vermaelen is likely to now be little more than an occasional back-up when he does return from the treatment room.
Barça will next be in action on Thursday in a city derby against Espanyol in the second leg of their Copa del Rey clash. Ernesto Valverde's team trail 1-0 from the first leg at the RCDE Stadium last week - their first loss of any kind since the Supercopa de España back in August.
After that, Barça finish January by facing Alaves in La Liga, before then meeting Espanyol again, this time in La Liga, to kick off the short month of February.