Granit Xhaka's place at the 2018 World Cup has been thrown into doubt after he suffered a knee injury in training for Switzerland on Thursday.
Images have emerged showing Xhaka being helped off the pitch, and he was taken to hospital for further scans to determine the severity of the injury.
He will definitely miss Switzerland's penultimate warm up match against Spain on Sunday and may face a race against time to be fit for his team's opening game of the World Cup against Brazil in Rostov on 17 June.
It would be a cruel blow for Xhaka, who enjoyed a clean bill of health for the whole of the 2017/18 season as he featured in every league game for Arsenal.
Xhaka has scored nine goals in 61 appearances for Switzerland since making his international debut in 2011. One of these came at the last World Cup when he scored in a 5-2 group stage defeat against France.
After the Spain friendly, Switzerland face Japan in Italy next Friday before travelling to their World Cup base in Togliatti.
After the opener against Brazil, Switzerland's remaining group games are against Serbia in Kaliningrad on June 22 and Costa Rica in Nizhny Novgorod on June 27.