The Germany star insists the 2013 Champions League finalists will continue to challenge in the Bundesliga in spite of their star forward's imminent switch to Bayern Munich.
Marco Reus insists there is life after Robert Lewandowski for Borussia Dortmund.
The Poland international is bound for Bayern Munich, after signing a pre-contract agreement with the European champions ahead of a summer switch to the Allianz Arena.
However, Reus says that BVB will get on with business as usual after their star striker heads for Bavaria.
"Robert Lewandowski is a great player, but he's made his decision and we've got to live with that," Reus told reporters. "Every player has to make his own decision. If that's where he sees his future, that's his future and Borussia Dortmund will go on without him."
The Dortmund star is realistic when assessing his side's prospects this season, though, with a 12-point gap to bridge to Pep Guardiola's irrepressible Bayern in the Bundesliga meaning that much of their focus may switch to the Champions League, in which it faces Zenit St Petersburg in the last 16.
"Everyone would agree that the Bundesliga is becoming a force to be reckoned with, and lots of top stars and top coaches are choosing to go there," added Reus. "I can't say why Guardiola chose to go there, but it's obvious that he has a good group of players to work with there. Bayern have played pretty much perfectly this season, which has made it hard for the other teams.
"It's obviously difficult to say that we want to catch Bayern because the difference is so great, but we want to try to make sure we at least get the second spot. But we're still in the Champions League and the German Cup so there's plenty for us left to play for. And in the Champions League, we have tricky opposition but we have the opportunity to progress."
Dortmund returns to league play after the winter break next weekend as it looks to reduce the five-point gap behind second-placed Bayer Leverkusen with a home win against Augsburg.