The Spain international has been linked with a potential move to the Bundesliga giants in recent weeks following a disappointing first season in the Premier League.
Morata failed to recapture his impressive form at Juventus and Real Madrid for the west London side after his £60m move from los Blancos last summer.
The 25-year-old made an impressive start to the season with eight goals in seven games but the Spanish striker suffered a loss of form and a string of niggling injuries.
Morata finished the 2017-18 campaign with 15 goals in 48 appearances in all competitions to raise questions about his future at Stamford Bridge.
Dortmund have sold Ousmane Dembele to FC Barcelona and Pierre-Emerick Aubameyang to Arsenal over the past 12 months to leave them somewhat lightweight up front.
Morata has been linked with a potential move to Dortmund to improve their options up front.
However, Dortmund sporting director Zorc ruled out a bid to sign the Spain international this summer.
“I would also say that Morata is too expensive – without knowing [the] exact sums,” Zorc told Spark Media Group.
“Of course, we have candidates in mind. But the position of centre forward is currently the most difficult to fill in European top football..
“That’s why we resisted selling Pierre-Emerick Aubameyang for a very long time because he guaranteed us goals.
“At the moment, I have the impression that the transfer market – not only in the case of strikers – is a bit out of touch with reality.
“We have to act with caution and not do crazy things.”
Morata was a late substitute in Chelsea FC’s 1-0 win against Manchester United in the FA Cup final last month.
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