The son of a miner, Baştürk began his football career at Sportfreunde Wanne-Eickel. As a teenager Baştürk played for SG Wattenscheid 09, and his breakthrough in the Bundesliga came with city rivals VfL Bochum, for whom he even played in the UEFA Cup. After the 2001 transfer to Bayer 04 Leverkusen, Baştürk was part of a team that finished second in the league, the DFB-Pokal and the 2002 UEFA Champions League Final in the 2001–02 season. Due to his role in Bayer's success and Turkey's third-place finish at the 2002 FIFA World Cup, Baştürk finished ninth in the voting for the 2002 Ballon d'Or.