Simms, who joined Sunderland on loan from Everton this summer, sustained an injury before the international break and missed the Black Cats’ 2-2 draw against Watford earlier this month.
Sunderland were hopeful that he would be fit to play after the international break but Mowbray conceded that the forward is still on the sidelines and will not be involved against Preston North End on Saturday.
The Sunderland boss conceded that it is likely ligament damage but insisted that everything is not in his hands.
He claimed that whether Simms will have to undergo further scans is a decision that is dependent on his parent club Everton.
Mowbray said in a press conference: “We had hoped Simms might be okay after the international break, but that is not going to be the case.
“We thought it was some ligament damage to his toe.
“He is on loan from Everton and they will decide whether he gets a scan now.”
Sunderland have made a solid start to their first season back in the Championship and are fifth in the league table.
Simms scored three times in his eight appearances for Sunderland before sustaining the injury and being without him is a blow for the Black Cats.
