Jack Ross has revealed Lee Cattermole missed the 2-0 win over Plymouth Argyle with a foot injury and is a doubt for the FA Cup game at Port Vale.
Cattermole suffered the injury against Shrewsbury Town and played through the pain barrier against Doncaster Rovers and Southend United.
Ross was keen for the problem not to develop so he wasn't involved and didn't travel to Plymouth, an Aiden McGeady brace sealing the victory that took Sunderland second.
Bryan Oviedo was also missing with a calf concern.
Josh Maja was recalled to the starting line-up but was subbed midway through the second half, he took a knock to his ankle first half but Ross doesn't think it is anything too serious and said that wasn't the reason he was subbed.
Ross said: "Bryan had a calf issue, Lee has an ongoing foot issue since Shrewsbury and to his credit he played through a lot of pain against Doncaster and in particular Southend.
"I think he may miss next week too but then may be back to fitness.
"We couldn't risk it flaring up and being more long term."
On Maja, Ross added: "He was limping a bit at the end of the game but hopefully it was just a kick and nothing more.
"It wasn't the reason we took him off, we just needed a bit of freshness."
With Peterborough United losing, Sunderland moved into second place and remain three points off leaders Portsmouth with a game in hand.