Lionel Messi's bid to surpass Gerd Müller's record of 85 goals in a calendar year is in jeopardy after the Barcelona attacker was carried off on a stretcher in their Champions League match with Benfica.
Messi arrived as a 58th minute substitute in the goalless draw but collided with the Portuguese side's goalkeeper Artur, injuring his knee in the process.
Barça announced Messi has "a bruise on the outside of his left knee" and will undergo further tests to determine the extent of his injury.
The 24-year-old has scored 84 goals for Barça and Argentina this year. He has four matches left this year to overhaul Müller's tally - La Liga games against Real Betis, Atletico Madrid and Real Valladolid, as well as a Copa del Rey tie with Córdoba.
Barcelona had already qualified as winners of Group G prior to their final fixture on Wednesday night, having lost just one of their six matches against Celtic last month.