Arsenal have confirmed that Brazilian Gabriel Martinelli will be out until the end of the year with a knee injury.
The 19-year-old forward, who joined from Ituano last summer, injured his left knee in training on 21 June.
Martinelli, who has scored 10 goals in 26 appearances in all competitions this season, has had surgery to repair a lesion in the cartilage of his knee.
Defender Pablo Mari is expected to return to training in September after spraining ankle ligaments last month.
An Arsenal statement on Martinelli said the teenager was recovering in a knee brace after his operation last month.
"He is currently at our training centre every day receiving specialist attention and support from our medical team and will continue his recovery throughout the close season, with the aim of a return to full training by the end of 2020," the Gunners said.