Career
During his career he played for 1. Willmer began his career with 1. Football Club Köln, and scored within two minutes of his Bundesliga debut for the club, a 5–1 defeat on the opening day of the 1977-1978 season.
Despite this inauspicious start, Köln went onto be German champions that year, with Willmer adding a further ten appearances.
By the 1979-1980 season Willmer had established himself in the Köln first-team, and helped them to another DFB-Pokal final, this time a 2–1 defeat against Fortuna Düsseldorf in which he appeared as a substitute for Pierre Littbarski. He spent one further season with Köln before joining Bayern Munich in 1984.
Willmer sat this match out, but featured in a second consecutive cup final - replacing Michael Rummenigge late in the game as Bayern did complete the double this time, beating VfB Stuttgart 5–1. Bayern also reached the European Cup Final, and Willmer was an unused substitute for the 2–1 defeat against Football Club Porto.
He left the club at the end of the season, joining Hannover 96, for whom me made 46 appearances over the next two seasons, retiring in 1989 after they had been relegated from the Bundesliga.