The 27-year-old Finland international striker would have been out of contract at Blues at the end of June and although the club had a two-year option on his contract he has confirmed that he will be playing his football in the German Bundesliga next season having agreed a three year deal with Hannover.
"I am looking forward to playing for Hannover and in the Bundesliga," Forssell has said.
Because of various injuries, Forssell has started just 44 games for Blues since moving from Chelsea three years ago on a permanent deal having previously spent a season on loan at St Andrews.
"We are very happy that we could persuade Mikael to join Hannover," their sporting director Christian Hochstatter has told his club's official website.Debut Apps (+ sub) Goals Yellows Reds 13 Aug 2005 44 (33) 18 1 0 06 Apr 2005 0 (2) 0 0 0 14 Sep 2003 39 (2) 19 1 0 09 Oct 2001 5 (30) 8 1 0 26 Feb 2000 53 (9) 15 0 0 1 (0) 0 0 0 First App. Apps (+ sub) Goals Yellows Reds 12 Aug 2007 23 (9) 9 0 0 05 Aug 2006 5 (5) 1 0 0 13 Aug 2005 16 (19) 8 1 0 14 Aug 2004 4 (2) 0 0 0 13 Aug 2003 36 (2) 19 1 0 09 Oct 2001 4 (30) 8 1 0 12 Aug 2000 40 (9) 15 0 0 13 Oct 1999 14 (0) 0 0 0