Arsenal winger, Gabriel Martinelli, was spotted on crutches following their 2-1 victory over Brentford in the Premier League on Sunday.
The Brazilian is now facing a race against time to be fit to play against Porto on Tuesday.
Martinelli was on the scoresheet as the Gunners thrashed Sheffield United 6-0 on Monday.
However, he got injured during the hour mark, following a heavy challenge.
Arsenal manager, Mikel Arteta, revealed after the game that the 22-year-old had merely sustained a heavy cut.
But the injury was serious enough for it to rule Martinelli out of the London derby against the Bees.
That victory was tempered slightly, however, by the news that Martinelli was seen by Football.London walking through the mixed zone after the match with the aid of crutches.