Dele Alli was taken off after 80 minutes in England's opening 2-1 Group G win over Tunisia.
England midfielder Dele Alli suffered a slight thigh strain in their opening 2-1 Group G win over Tunisia and the injury will have to be managed over the coming days, the FA said on Twitter.
The 22-year-old seemed to pull up with a muscle problem in the first half, with Fabian Delph getting ready to come on, but Alli managed to continue until being taken off after 80 minutes.
The Tottenham Hotspur player had a scan on Tuesday while his team mates trained after picking up the strain in Volgograd.
"We had to keep monitoring Dele," England manager Gareth Southgate said on Monday. "He was feeling a little bit of an issue just before halftime, but he felt he could carry on."England play their second match on Sunday in Nizhny Novgorod against Panama, who lost 3-0 to Belgium in their opener.