Ethan Nwaneri looked to have solved the issue on the right-hand side of Arsenal’s attack, following the injury to Bukayo Saka.
The 17-year-old started his first Premier League game in the 3-1 win over Brentford and impressed with a positive performance.
Nwaneri then started and scored the opening goal in the 1-1 draw with Brighton but did not appear after half-time.
Mikel Arteta was asked why the attacking midfielder didn’t come out for the second period, with the manager revealing that he is now on the lengthy injury list at Arsenal.
“Really bad news because I think we have lost him. We had to take him off at half-time with some muscular issues,” Arteta said.
The Gunners are already missing Saka with a long-term hamstring injury and Raheem Sterling with a knee injury. Kai Havertz missed the game at Brighton with illness and captain Martin Odegaard was only well enough for the bench, after also suffering with illness.
Arsenal play Newcastle in the semi-final of the Carabao Cup on Tuesday night at Emirates Stadium.