Simms, who is on loan from Everton, scored three goals in eight games so far this season before suffering a toe injury in the game against Reading in September.
Up until Stewart’s injury during the warm-up before the Middlesbrough match, the striker had been Sunderland’s most consistent player, scoring five goals and laying on three assists in seven Championship games.
Mowbray’s men will travel to Blackburn to take on Jon Dahl Tomasson’s side on Tuesday and yet again will miss their striking duo against the Riversiders.
Sunderland have scored five goals in five matches since the absence of both strikers, and Mowbray admitted that it is a challenge for his side to score without them.
Mowbray stressed that his team need to find ways to keep scoring against their opponents and believes that everyone in his squad needs to step up in the absence of Simms and Stewart.
“The narrative of the questioning and story is that we can’t score without strikers, and yet we have to find a way and we can score without strikers”, Mowbray said at a press conference.
“It’s different types of goals and I thought the first goal against Wigan was a really good goal.
“We created an overload, switched the play and Dennis got past Pritchard, cut it back and we scored.
“I think we can score them types of goals and score individual goals, Patrick Roberts has done that a few times with his individual talent.
“They all have to step up and hopefully in the next few weeks the strikers return and we have different options for different games.”
Tomasson’s Blackburn Rovers are in sixth place in the league table and have not lost in their last four home games against Sunderland.
