World number eight Fish advanced to the final with a 6-3 6-4 victory over the Serbian in Montreal and Tipsarevic has declared his disappointment at his performance.
"It's been a great week for me but I am really not happy with my performance today," said the world number 46.
"I didn't feel tight before the match and I didn't have the feeling that this was the biggest match of my career, I wasn't nervous.
"I just felt I was too focused on fighting for every point rather than being focused on what I needed to do on court."
The 27-year-old has yet to win a title during his career.