Vito Mannone is to undergo a scan on an arm injury amid concerns he may have suffered a fracture.
Sunderland manager David Moyes revealed the goalkeeper was travelling to hospital on Tuesday afternoon to undergo checks after being hurt in training.
Mannone, 28, was not due to play in Sunderland's EFL Cup second round tie away at Shrewsbury on Wednesday night, with England under-21 international Jordan Pickford set to start in goal.
However, with Sunderland still chasing their first point of the Premier League season and having already said his side are in a relegation battle, Moyes will be hopeful the former Arsenal man will be available to face Southampton on Saturday.
Mannone started both of the Black Cats' opening top-flight fixtures this season and has made 59 appearances for the north-east club since arriving in 2013.