Middlesbrough defender Matthew Bates suffered an injury scare during last night's friendly against Darlington.
He told the Northern Echo: "It is a concern because the way he fell didn't look very good.
"We'll scan it in the morning and fingers crossed it's not serious but I must say it didn't look good.
"It is not the same injury as before as it was the other leg. The pitch was slippy and it looked like he lost his footing."