The Germany internationals were withdrawn in the second half of the clash at the Weserstadion, which marked Dortmund's second straight Bundesliga win after a run of four top-flight games without victory.
And the club confirmed on their official Twitter account on Sunday that they expect to be without Reus for around a fortnight and Bender for a week.
"Marco Reus retired in the game in Bremen (due to) a torn muscle in his right thigh and is expected to be (out for) two weeks," Dortmund stated.
"Sven Bender has (injured) a muscle in his right thigh in the game and is expected to (be out for) one week."
Both players will therefore miss Dortmund's DFB-Pokal clash with Eintracht Frankfurt on Tuesday, with Bender potentially being fit for their league fixture at home to the same opponents next weekend.
Reus, meanwhile, could return against struggling Hamburg on February 22.
Dortmund coach Jurgen Klopp will hope to have the pair back fully fit when they resume their UEFA Champions League campaign against Zenit St Petersburg three days later.
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