Thomson suffered head blow
Tony Mowbray revealed that Kevin Thomson was knocked unconscious during Middlesbrough's 2-0 home defeat to Leeds.
The Scottish midfielder emerged as a 62nd-minute substitute but soon found himself being carried off the field on a stretcher after taking a boot to the head.
But the Boro boss expressed his relief that Thomson had come round shortly after the match, which was decided by goals from Robert Snodgrass and Luciano Becchio.
"He was out cold, he got knocked out and wasn't conscious," said Mowbray. "But he's come around now and seems OK, but we've got to be very, very careful with concussion.
"I think Kevin's just had a dreadful time since he's come here. First he broke his leg on a treadmill at home and then it's been injury after injury after injury.
"He's had an illness for the last fortnight and had just got himself ready to come back into the team but he's off again within 10 minutes. I'm sure he'll go through a spell where he'll show everybody what a quality player he is. He's a high quality player and I'm sure at some point in the future he'll show everybody what a talent he is."