The midfielder is adamant the Polish striker will still give his all for the club despite frequent rumors linking him with a move to Bayern Munich.
The Poland international was close to joining Bayern Munich this summer, but the deal fell through as BVB CEO Hans-Joachim Watzke decided to keep the star for another season. Lewandowski's contract with Jurgen Klopp's side expires in June 2014 and he has already intimated he could join Bayern at the end of next season.
"We have a superb team with a great atmosphere among the squad," Bender told reporters at a press conference in Bad Ragaz. "Robbie is committed and gives everything. He's the same he has always been."
Bender then went on to praise "the fastest offense" he has ever played behind but warned that his team should also focus on stabilizing the defense as well to avoid conceding as many goals as last season.
"If you concede less, you need to score less in order to win. Therefore, we must act focused and disciplined at the back," Bender said. "If we're able to do that, we can beat any opponent."