The defending German champions are currently 11 points behind leaders Bayern Munich in fourth.
"I think the current table situation will not be the same at the end [of the season]," said the 32-year-old.
"There are still a lot of matches to be played, and we still have half a year in front of us.
"We will keep on believing in our ability to finish in a top position. We certainly do have the potential and therefore the season for us is far from over."
Dortmund won the Bundesliga title in 2011 and 2012.