Andreas Bjelland was forced off at half-time in Brentford's draw with Derby after suffering a tight hamstring, Dean Smith confirmed after the game.
The Dane was replaced by youngster Chris Mepham, making his maiden league appearance, and the 19-year-old produced an assured performance as Brentford pushed for an equaliser.
And Smith hailed the character of the centre back who, after his struggles against Norwich, was understandably nervous before coming on.
“Andreas has got a tight hamstring and we couldn't risk him pulling the hamstring,” Smith confirmed.
“Meps had a tough baptism of fire last week against Norwich. A penalty against him after 10 minutes and a poor performance from us.
“The performance will give him a big boost. I know he was nervous at half time about to go on but I've got great belief in the ability of the player.”
John Egan missed the game with concussion, sustained in the 3-0 win at Bolton on Saturday, but Smith confirmed he would be available for Saturday's trip to Middlesbrough.
He added: “Apart from a fat lip and a couple of stitches in there. He was groggy and with the concussion rules at the moment, we couldn't risk playing him tonight.
“We've had two concussions in two weeks which is unheard of. He's back to base line so he'll be fine for Saturday.”