The BVB official has insisted "nothing is settled" on the eve of facing Real Madrid and believes the team deserve more credit for their heroics in the first leg
Die Schwarzgelben bring a healthy aggregate lead to the Bernabeu after the Liga giants were humbled 4-1 at Signal Iduna Park on Wednesday, prompting many to believe the second leg is a mere formality for Jurgen Klopp's men.
Despite the advantage Watzke says he is in for an anxious 90 minutes because he insists Mourinho's men boast the home form necessary of staging a remarkable comeback.
Speaking to reporters, he said: "I know that we've built a solid foundation, but nothing is settled yet. Real Madrid are very strong at home, so I'm a little bit tense at the moment.
"We'd like to play [in the final at] London of course, so I'm a little bit nervous."
With Robert Lewandowski netting all four goals in the first leg victory, speculation has since intensified over where the Poland international will be plying his trade next season.
And Watzke has hit out at media outlets for placing too much emphasis on the future of certain BVB stars while ignoring the resounding 4-1 win.
"During the last week there has been a lot of speculation on which players might appear for a different club next term instead of giving credit to the team's performance," he added. "A lot of these obscure rumours were overrated by the media."
Tuesday's match at the Santiago Bernabeu is scheduled to kick off at 20:45 CET.