Everton have confirmed that Muhamed Besic will be assessed to determine the extent of the leg injury that he picked up against Swindon Town.
The midfielder was forced off during Saturday's friendly at the County Ground after pulling up while running.
Everton went on to win the match 4-0, with all four of their goals coming in the second half.
Besic is due to be assessed on Sunday to see whether he is fit enough to travel with the team to Singapore next week for the Premier League Asia Trophy.
Everton start their Premier League campaign at home to Watford on August 8.