Gabriel Martinelli sustained a serious ankle injury in the warm-up prior to Arsenal's FA Cup clash with Newcastle, with the Brazilian forced to miss the match.
Martinelli had been originally named in the starting XI for the third-round tie against Newcastle on Saturday, but appeared to roll his ankle as he warmed up, pre-match.
The Brazilian appeared to be distressed as he received treatment from the Arsenal medical staff, before getting to his feet.
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He was replaced in the Arsenal starting XI by Reiss Nelson, after the club confirmed it was an ankle injury that Martinelli had suffered.
The forward will have a scan on his ankle in the next 24 hours.
Emile Smith Rowe scored an extra-time winner for the Gunners at the Emirates Stadium which secured the FA Cup holders a place in the fourth round of this season's competition.
After the game, Arteta said: "I am gutted. I was in my office before the game and one of the medical staff came in and said he twisted his ankle.
"He was in tears and in a lot of pain. I'd imagine it's going to be bad news but we'll wait to see what's going on."
The fresh setbacks comes as a blow to Arsenal and Martinelli. The 19-year-old has helped Arsenal turn their season around in recent weeks, after returning from a long absence with a knee injury.