In the 2004–05 season, he played 28 times and scored six times for the Regionalliga (third division) team of VfB Stuttgart.[2] In the same season, he had his Bundesliga debut against Hertha BSC on 20 February 2005 (1–0). He scored his first goal in a UEFA Cup game against Domžale on 25 September 2005.
In 2006, Gentner's contract in Stuttgart was extended until 2010.
On 18 July 2007, he was loaned to VfL Wolfsburg until summer 2009 and on 11 August 2008 Gentner signed a permanent deal with Wolfsburg.[3]
On 8 January 2010, Gentner announced that he would be joining VfB Stuttgart[4][5] at the end of the season. After seeing out his contract with the Wolves which ended on 1 July 2010, Gentner returned to Stuttgart on a free transfer.
On 6 January 2013, Gentner extended his contract with VfB Stuttgart until June 2016 with an option for a further year.[6] Following Serdar Tasci's departure to Spartak Moscow, it was announced that Gentner is to be his successor as the new club captain.[7] In May 2016 Gentner extended his contract with VfB Stuttgart until June 2019.[8]
On 5 July 2019, Gentner signed a contract with club Union Berlin.[9]
In September 2022, Gentner announced that he would retire from playing at the end of 2022.[10] At the same time, VfB Stuttgart announced that he would join the club on 1 January 2023 as head of the professional player department.[1]
International career
On 19 May 2009, Gentner was called up to the senior Germany national team for their tour of Asia.[11] He made his début against China on 29 May 2009.[12] Until August 2010 he won five caps in total.[13]
