Blaszczykowski has been ruled out for the rest of the season having torn his anterior cruciate ligaments during Saturday's 2-2 draw with Augsburg.
"We have talked internally and looked at the market. I won't rule out that we will be active again after Blaszczykowski's injury. However we will only do that when it makes sense financially as well as in sporting terms," Watzke told Die Welt.
Dortmund currently sit third in the Bundesliga table, 14 points behind leaders Bayern Munich.