Arsenal suffered an injury blow when defender Kieran Tierney was forced off with what looked like a shoulder problem during the first half of Monday night’s Premier League clash with West Ham.
The Scotland international appeared to suffer the injury after colliding with Michail Antonio while defending a West Ham free-kick.
He was replaced by Sead Kolasinac, who was only promoted to the bench half an hour before kick-off when Hector Bellerin suffered an injury in the warm-up.
Tierney was making just his ninth start of the season after struggling with a number of injuries since his £25 million ($30m) move from Celtic in August.
The 22-year-old arrived still recovering from a hip injury that required surgery over the summer, meaning he was unable to make his debut until a Carabao Cup win over Nottingham Forest in late September.
However, he has continued to struggle with his fitness and so has failed to hold down a regular place in the side.
He withdrew from the Scotland squad for last month’s Euro 2020 qualifiers to work on his fitness and it was hoped he had put his injury woes behind him.
It was reported in the build-up to Monday’s game that Tierney had been battling a shoulder issue, though he was deemed fit enough to start his first game under interim boss Freddie Ljungberg in east London.
The Swede, though, must have been concerned at the sight of the defender in clear discomfort, with his shirt supporting his right arm like a makeshift sling.
As well as assessing Tierney, the Gunners will also check on the fitness of France full-back Bellerin, who himself has been restricted to just seven appearances this campaign as he continues his return from an anterior cruciate ligament injury.
Granit Xhaka then became the third casualty of the evening when he was forced to come off with a head injury in the closing stages.