On 6 August 2005, at the age of 16 years and 334 days, Şahin set a record by becoming the youngest player to have played in the Bundesliga (this was later surpassed by Youssoufa Moukoko on 21 November 2020 at the age of 16 years and 1 day). On 25 November of the same year, Şahin became the youngest player to score a goal in the Bundesliga, scoring for Borussia Dortmund against 1. FC Nürnberg (this was later surpassed by Florian Wirtz on 6 June 2020 at the age of 17 years and 34 days).