Andreas Sassen began in Schwarz-Weiß Essen playing football at the club. In 1990 he moved to FC Bayer 05 Uerdingen. In the 1990/91 season Sassen debuted in the first division. For the Krefeld he played 66 league matches, scoring a total of 12 results. Of these, 35 games ( 5 goals) in the 1st Bundesliga and 31 games (7 goals) in the 2nd Bundesliga.
In 1993, Andreas Sassen signed a contract with the North German tradition club Hamburger SV, in which he played until November 1994. The big break he was not able at the HSV (38 Bundesliga matches / 1 goal). In the season 1993/94 he was part of the permanent staff of the Hamburg, but already in the season it was the HSV midfielder to Dresden pull. He played six games ( no goals ) in the 1994/95 season for the first FC Dynamo Dresden, which had to be the last of the 1st Bundesliga descend from the upper house, and after the withdrawal of the license for the 2nd Bundesliga in the Regional found again.
Sassen tried his luck in the Ukraine in Dnepropetrovsk Dnieper. He acted in the highest Ukrainian League for the team from Dnipropetrovsk in eleven matches ( no goals ). In the 1995/96 season he was active the last time in German professional football. For the SG Wattenscheid 09, he completed ten games in the 2nd Bundesliga, where Sassen once hit the opponent's goal. Thereafter, the midfielder kicked briefly in his parent club Schwarz-Weiß Essen in amateur, before his career ended because of problems off the field. Overall, he played 79 games ( six goals) in the 1st Bundesliga and 41 games (8 matches ) in the second league.
In the last years of his life Sassen was employed as an assistant gardener at the Parks Commission of the City of Essen. He died 36 years old from a stroke.
Sassen was considered one of the greatest talents in German football, but had significant alcohol problems, which not only multiply the license cost him, but also repeatedly led to the dissolution of his employment contract.