Lewandowski speculation angers coach Klopp
Lewandowski, whose Dortmund contract runs out in 2014, has so far refused to sign an extension and has been linked with a move to rivals Bayern Munich, who currently lead the title race by 17 points.
Media reports suggest Lewandowski could delay a move until 2014, so he could he could join Bayern without a transfer fee, while the player said this week he would see out his contract at Dortmund.
"Why don't you ask me about [Bayern strikers] Mario Gomez and Arjen Robben and where they will be playing next season," Klopp told reporters. "We could be talking about other things as well.
"I can understand that people make a big deal out of it but for us it is a normal situation. We will not get stressed out by this. Robbi is with us.
"If someone wants him they can say so and then we can think about it. If there is no one there then he will continue playing for us. It's as simple as that."
Champions Dortmund are looking to bounce back from Wednesday's 1-0 German Cup quarter-final defeat to Bayern and are eager to hold on to second place in the Bundesliga.
It was Dortmund's first defeat in seven games to Bayern and means they realistically have only the Champions League left to play for.
"You cannot win the Bundesliga title every year," Dortmund defender Neven Subotic told reporters. "We are out of the cup and we will now be looking to do well in the league.
"Obviously we will be watching out for those teams that have the same targets as us and that is a spot in the Champions League," he said conceding Bayern were too far ahead to be caught.
With only a point separating them from third-placed Bayer Leverkusen, Dortmund are eager to return to winning ways as soon as possible.
Hannover, in seventh on 33 points and with a Europa League spot firmly in sights, will be no pushover after last week's 5-1 win over Hamburg SV.
"We are back to playing well. Our curve has an upward trend," said Hanover centre-back Christian Schulz. "These games are absolute top games and we are ready to frustrate the champions."
Bayern travel to relegation-threatened Hoffenheim on Sunday, having won 19 out of 23 league games so far, conceding just eight goals.
With Franck Ribery back in the squad, after he was suspended for the cup, it remains to be seen whether Arjen Robben will also feature for coach Jupp Heynckes.
The Dutchman scored the winner against Dortmund but has spent much of the season on the bench and has been vocal about his frustration.
Leverkusen host VfB Stuttgart, who are chasing a European spot and are buoyed by their German Cup quarter-final victory over second-tier VfL Bochum on Wednesday.