Arsenal boss Mikel Arteta says new signing Mikel Merino will be out for a "few weeks" after injuring his shoulder during his first training session with the club.
The Spaniard completed a £31.6m move to the Gunners from Real Sociedad on Tuesday.
Merino, Arsenal's second signing of the summer following the arrival of Riccardo Calafiori from Bologna, trained with his new club for the first time on Thursday.
The 28-year-old collided with a team-mate, resulting in a "small fracture" that will keep him out for a "few weeks".
"Very unfortunate yesterday he had a collision and he has got a shoulder injury, unfortunately.