He started his professional career as an assistant coach for German legend Horst Hrubesch in Samsunspor in 1997.
In that division he grew to a reliable hitman, scoring 71 goals for Rot-Weiss (at times alongside Horst Hrubesch) until the end of the 1981 season, forty of those just in his 38 appearances of 1979–80.
While the score was tied at 4-4, Bossis missed the next penalty, allowing Horst Hrubesch to score the last penalty and drive the Germans to the final.
Louis Horst | Horst Liepolt | Horst Hrubesch | Horst Köhler | Horst | Horst Schumann | Horst Buchholz | Horst Wessel | Horst Stein | Horst Muhlmann | Horst Jankowski | Horst Bredekamp | Horst aan de Maas | Hans Horst Meyer | Horst Heese | Horst H. Baumann | Horst Fascher | 18th SS Volunteer Panzergrenadier Division Horst Wessel | Horst Zuse | Horst Wohlers | Horst-Wessel-Lied | Horst von der Goltz | Horst Steinmann | Horst Schmid | Horst-Rüdiger Schlöske | Horst Rosenkranz | Horst Niemack | Horst Mahler | Horst Lippmann | Horst Kwech |
With Horst Hrubesch, Felix Magath and Manfred Kaltz, Hamburg pulled off one of the biggest upsets in European Cup history by beating a Juventus side packed with Italian players who had won the World Cup a year earlier and two star import players – Michel Platini and Zbigniew Boniek.