The 20-year-old midfielder nearly joined Bremen in 2012 from Karlsruher before the Bundesliga club cancelled the deal over problems surrounding the transfer fee.
Calhanoglu, who scored an incredible long-range free-kick against Borussia Dortmund last Saturday, signed for Hamburg instead and admits scoring against Bremen will be sweet, both on a personal level and to please the club's fans.
"I am very happy that I am in Hamburg," he told Bild. "I'm going into the derby with excitement because we need the points.
"At the time (2012) I felt ripped off by Werder. They did not call me.
"The fact that Bremen has made whatever reason but not told me was bad. That was disrespectful."
Victory over Dortmund was Hamburg's first in the league since November and came in Mirko Slomka's first game in charge after replacing Bert van Marwijk.
Calhanoglu thinks Slomka lifted morale ahead of the Dortmund clash and wants more of the same on Saturday to ease Hamburg's relegation fears.
"We were all previously somehow blocked in the head (under Van Marwijk)," he added. "The coach (Slomka) has brought back the laughter and the fun.
"The mood is good, that is very important to us.
"We want to have success again."
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