Arsenal are sweating on a knock suffered by Lucas Torreira in action with Uruguay on Saturday.
The Gunners midfielder was replaced after just 45 minutes - and was then pictured wearing an ice pack on his left leg on the bench during their 4-1 friendly win over Mexico.
Torreira, a £22m signing for Italian side Sampdoria, has been eased into coach Unai Emery's starting side after a delayed return from the World Cup.
He has made an appearance from the bench in all four of Arsenal's opening Prem games - while his most recent cameo display against Cardiff has had fans calling for him to start against Newcastle.