He therefore had an unusually low centre of gravity, which enabled him to protect the ball in the box against much bigger defenders and turn around quickly for close-range shots.

In the German Bundesliga he played 350 matches for Bayer 04 Leverkusen and scored 182 goals (ranked #7 in the all-time top scorer list).

He established himself as one of the most dangerous strikers in the Bundesliga, but Bayer Leverkusen regularly ended as runner-up to either Bayern Munich or Borussia Dortmund.

Off the pitch, Kirsten was famous for his strong beard growth, which earned him a sponsorship by Braun, who used him to advertise their electrical shavers.

[3] Along with several other teammates, Kirsten was allegedly implicated as an Stasi informant during his time at Dynamo Dresden through files recovered from the security service's archives after the fall of East Germany.