The Ospreys are sweating over the fitness of Wales international duo Adam Jones and Ryan Jones for the upcoming derby against the Scarlets.
It is touch and go whether the prop and back-row forward will be fit for the September 21 fixture, with current knee issues causing the pair problems.
Jones and Jones have yet to take to the field this season and will miss this week's fixture against Glasgow at Liberty Stadium, with Ospreys head coach Steve Tandy explaining the situation.
"Adam would have been involved this weekend on the bench, but he has a bump on his knee from last Tuesday. He will probably miss this weekend and potentially the Scarlets," he told BBC Sport.
"But we have been pleased with Aaron Jarvis who has responded and has been playing really well.
"Aaron will start again this weekend and that is a positive for him and for us knowing we have a bit of strength-in-depth at tight-head."
On the fitness of former Wales captain Jones, Tandy was enthused by his progress.
"Ryan is looking really good in training," said Tandy.
"He is up and running and is an outside chance for being involved against the Scarlets. If not, he is highly likely to be involved against Munster the week after."