Tony Mowbray says Rovers will cross their fingers for Scott Wharton, but the boss feels the defender's injury won't be a short-term fix.
The centre back, returning to the team at Brentford, went down early on in the game in west London clutching his calf.
He was forced off on a stretched just a couple of minutes prior to Joe Rothwell's opener at the Brentford Community Stadium.
And Mowbray's initial diagnosis isn't a positive one regarding the Blackburn-born defender's setback.
“Scotty Wharton looks as if his Achilles is causing him trouble," he revealed to iFollow Rovers.
“It’s really worrying when he goes down with no trouble and no player around him.
“Why does Scotty break down? I’m not sure if it’s down to fatigue because he missed the last game.
“It’s a real concern for us, particularly in that position.
“The doctor travels with us every game and Scott’s injury will need a scan, but it’s never a good sign.
“The doctor’s said to me that it feels pretty loose, and without being overly negative, it doesn’t seem that it’s a mild injury. We’ll know more when he goes for his scan.”