The director refuses to entertain the possibility of an overseas owner ever taking over his club, citing the recent troubles at Malaga as the main reason behind his stance
Current rules in the Bundesliga stipulate that all of its members must be at least 51 per cent owned by club members, meaning a third-party investor would not be allowed to take overall control of a side.
However, the significant backing of Sheikh Mansour has allowed Wednesday's opponents to become a European force in recent years but despite their sudden growth, the Dortmund CEO has no interest in sanctioning such ownership.
"I would not even welcome him," Watzke told reporters. "Maybe at other clubs, but what if the sheikh, as shown by Malaga, lost interest? Then it becomes critical.
"The fact is that the Bundesliga has caught up considerably, thanks to their sound banking practices. This will eventually be expressed by [winning] results."
Watzke then came to the conclusion that European football is more difficult due to the higher standard of defences, thereby putting a greater onus on taking chances.
"There will not be many goals," he claimed. "At European level, you do not get as many opportunities as in a normal league game."
Meanwhile, BVB coach Jurgen Klopp assured that his side have devised a plan to stop their English opponents in the Champions League, despite the array of big names that they have in their ranks.
"Manchester City are really strong and are peppered with absolute superstars. However, we have a plan," he was quoted as saying by Bild.