Arsenal boss Arteta reveals new signing Mikel Merino injures shoulder 

Arsenal boss Mikel Arteta has revealed new signing Mikel Merino has injured his shoulder during his first training session with the club.

Speaking at the club's training ground London Colney, the Gunners manager admitted the £31.6m signing from Real Sociedad earlier this week will be missing for a minimum of "few weeks" after sustaining an injury to his shoulder.

The news is a big blow after the Spaniard only completed his move to Arsenal from Real Sociedad on Tuesday.

The 28-year-old midfielder collided with a team-mate, resulting in a "small fracture" that will keep him out for a "few weeks".

"Yes, very unfortunate," said Arteta,adding: "Yesterday [Thursday] he had a collision and he has got a shoulder injury, unfortunately. It looks like he is going to be out for a few weeks," said Arteta.

"He was really excited and everything was looking really good. He landed on the floor and Gabi landed on top of him and it looks like he has a small fracture probably.

"We have to see. He was in so much pain, we have to wait to do some more tests."

The injury is frustrating for Merino, Arsenal's second signing of the summer after the arrival of Riccardo Calafiori from Bologna, only trained with his new club for the first time on Thursday.

Arteta refused to be drawn on the prospect of Raheem Sterling joining the club before the transfer window closes on Friday evening, preferring to focus on Arsenal's Premier League clash with Brighton this weekend.

Arsenal have won both of their opening Premier League fixtures, beating Wolves and Aston Villa.

The Gunners host Brighton - one of the other three teams in the division with a 100% record so far this term - at the Emirates on Saturday lunchtime.

The Seagulls have suffered an injury blow of their own with Matt O'Riley, the south coast club's £25m new arrival from Celtic being being injured a matter of minutes into his debut for Brighton. 

The 23-year-old was hurt in a tackle by Crawley captain Jay Williams six minutes into his debut in the Carabao Cup second round.

Brighton's 31-year-old boss Fabian Hurzeler said: "It is like we expected, it is a bad injury and he needs surgery on his ankle."