Kaufmann joined FC Basel's first team for their 1902–03 season. He played his domestic league debut for the club in the home game on 2 November 1902 as Basel were beaten 1–4 by FC Bern.[1] Kaufmann played six of the eight league matches that season and the team finished the group stage in third position in the league table.
Kaufmann was also regular starter in the following two seasons. He scored his first goal for his club on 27 November 1904 in the home game in the Landhof as Basel won 3–0 against Weissenbühl Bern.[3]
During his three seasons with the team, Kaufmann played at least 23 games for Basel scoring two goals. 17 of these games were in the Swiss Series A and six were friendly games. He scored one goal in the domestic league and one was scored during the test games.[4] He probably played in more games than mentioned, but the documentation is incomplete.[note 03–04 1][note 04–05 1]