Mikel Merino is injured and is set to miss the next few weeks of action, according to Arsenal boss Mikel Arteta. The Spain international recently touched down from Real Sociedad, becoming the Gunners’ second summer signing after defender Riccardo Calafiori. Arsenal had been hoping to unleash Merino in their Premier League showdown with Brighton on Saturday (12.30pm). However, Arteta has now confirmed the 28-year-old is injured and set to miss the next few weeks in a huge blow for his side. “Very unfortunate yesterday (Thursday) he had a collision and he has got a shoulder injury unfortunately,…