Sunderland manager Martin O'Neill admits Phil Bardsley is struggling to be fit for Sunday's Tyne-Wear derby at Newcastle United.
Bardsley picked up a calf injury during last weekend's defeat by West Brom and subsequently missed Scotland's friendly with Slovenia.
The 26-year-old is undergoing intensive treatment ahead of the trip to St James' Park so Craig Gardner and John O'Shea are on standby to step in at right-back.
"Phil felt really tight in his calf after the West Brom game," O'Neill told the Newcastle Chronicle.
"He informed the Scottish FA, but obviously they wanted him to travel up so he did that and they realised there was something wrong with him after all.
"At this minute, if the game was (Thursday), he'd be really struggling, which would be a big blow."
Goalkeeper Keiren Westwood is struggling (wrist) so Craig Gordon is set to be included on the Black Cats' bench for the first time since last April.