PHOTO: AFP
"We have always found solutions and we will find solutions again," said Watzke after reports that Hummels is the latest Borussia star to be offered a contract at rivals Bayern Munich.
"It doesn't matter what a player decides to do, we have shown in the last five years that we can replace everyone."
The 27-year-old has a year left on his Dortmund contract, but last week Hummels' father refused to rule out a return to Bayern, from whom he joined Borussia in 2008.
Dortmund book final date with Bayern
Hummels could follow Germany's World Cup winner Mario Goetze, who left Borussia for Bayern in 2013, and striker Robert Lewandowski, who quit in 2014, on what is becoming a well-worn path from Dortmund to Munich.
But Borussia hope to keep hold of Hummels.
"We are having confidential discussions with Mats," Dortmund's director of sport Michael Zorc told Sky before Saturday's 3-0 league win at VfB Stuttgart.
"But we don't want to comment further on this subject, because nothing has yet been decided."
Dortmund homecoming for Liverpool's Klopp
Dortmund are seven points behind Bayern with three games left and Germany's top two teams will meet in the German Cup final on May 21.
Hummels, just as he did at the same stage of last season, has openly admitted he is considering his options having been linked to the likes of Bayern, Barcelona and Manchester United.
"It is a very difficult decision. When I make it at some point, then everyone will understand why it is so difficult for me," he said on the subject.
"It has been costing me about half an hour of sleep per night before I drift off, because the issue is so close to my heart."
COMMENTS
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ