Knup played his youth football with local team
Basel. He advanced to their first team for their
1985–86 season and signed his first professional contract under manager
Helmut Benthaus. After playing in one test match, Knup played his domestic league debut for the club in the home game at the
St. Jakob Stadium on 19 April 1986 as Basel won 5–0 against
Baden. In his first season Knup had just seven league appearances. During their
1986–87 season Knup advanced and became a regular in the starting team. Knup was a typical No. 9 and was famed for the power he could get behind his headers. He scored his first league goal for his club in the first game of the season on 9 August 1986. It was the last goal of the away match against, but it could not help the team, as Basel were defeated 1–3 against
Sion. In the following match one week later Knup played three seasons with the club and received a call up to the
Switzerland national team. But with Basel, apart from one title in the
Uhrencup in 1986, he had no big successes. In their
1987–88 season his teammates included goalie
Urs Suter, the defenders
Peter Bernauer and
Massimo Ceccaroni, the Scott
Gordon Duffield Smith and two other Switzerland national team players
Peter Nadig and
Dominique Herr. Despite this personally strongly occupied team Basel were relegated to the
Nationalliga B after the
1987–88 Nationalliga A season. One match in this season receives a particular mention, the away game on 29 November 1987 and Knup netted a hat-trick between the 37th and 71st minute as Basel won 4–0 against
Zürich. Following the relegation he left the team and joined
FC Aarau in 1988. He spent only one season at Aarau and signed for
FC Luzern in 1989 where he was an immediate success. In 1990, he was voted Luzern's
Player of the Year. He was then signed by
Bundesliga side
VfB Stuttgart in 1992 where he played until 1994 when he signed for
Karlsruher SC. He reached the
1995–96 DFB-Pokal final with Karlsruhe but they were beaten 1–0 by
1. FC Kaiserslautern. He then had a short spell with
Galatasaray S.K. in Turkey before returning to Switzerland. During the winter break of their
1996–97 season Knup returned to his club of origin under manager
Karl Engel. But Knup needed some six matches before he found the binding to his new teammates and then it came to being. He scored two goals at home against
Grasshopper Club, another goal in the home match against
Xamax and another two goals in the home match against
Aarau. Knup stayed with the club for another season before he retired from his active football career. Between the years 1982 to 1988 and again from 1996 to 1998 Knup played a total of 138 games for Basel scoring a total of 54 goals. exactly 100 of these games were in the
Nationalliga A, eight in the
Swiss Cup and 30 were friendly games. He scored 29 goals in the domestic league, four in the cup and the other 21 were scored during the test games. ==International career==