Stoke City attacker Marko Arnautovic could reportedly be heading for a period on the sidelines after suffering a potentially serious knee injury during his team's pre-season victory over Swiss side Neuchatel Xamax on Monday.

It is understood that Arnautovic has handed in a transfer request at Stoke, but the 28-year-old started his club's pre-season friendly with Xamax after travelling to Switzerland with the Potters squad.

The Austrian international was forced off shortly before the interval, however, and according to Sky Sports News, Stoke are fearful that the unsettled forward has sustained a long-term problem.

Stoke chairman Peter Coates recently revealed that the club have rejected a £15m bid from West Ham United for Arnautovic, who scored seven times in 35 appearances for the Potters during the 2016-17 campaign.

The attacker's reported unhappiness at Stoke is said to be due to having "grown increasingly frustrated with what he sees as a lack of ambition at the bet365 Stadium".