|Date of birth||4 October 1988|
|Place of birth||Nürtingen, West Germany|
|Height||1.84 m (6 ft 1⁄2 in)|
|2007–2008||Stuttgart Kickers II||40||(3)|
|2009–2010||Eintracht Frankfurt U23||29||(0)|
* Senior club appearances and goals counted for the domestic league only.
Thomas came through the youth system at VfB Stuttgart. In 2007 he was signed by Stuttgart Kickers. In the 2007–08 season he played for their reserve side Stuttgart Kickers II, who play in the Geman Oberliga. In the 2008–09 season he was promoted to the first team, and made 18 appearances in the professional 3rd Liga.
In 2009–10 he played for Eintracht Frankfurt U23 in the fourth tier Regionalliga Süd. By 2010–11 he was back in the 3rd Liga with TuS Koblenz, playing 37 games and scoring twice in the league, and making a further three appearances in the DFB-Pokal cup. Both league goals came in a 3–2 victory over SV Wehen Wiesbaden. Although the team finished the season in 11th place, they were not granted a 3rd Liga license for 2011–12 as a result of financial problems. Effectively relegated, they will instead compete in the fourth tier Regionalliga West. Thomas left the club in June 2011. Kickers Offenbach made an approach to sign the player in the same month, but this was withdrawn when the player took too long to demonstrate a commitment to join the 3rd Liga side.
In July 2011, he joined Scottish Premier League side Aberdeen for a trial at their pre-season training programme in Netherlands and Germany. On 6 July 2011 he played for Aberdeen in a friendly match against Bundesliga II side VfL Bochum, crossing for Darren Mackie to score Aberdeen's only goal in a 2–1 defeat. The following day, however, manager Craig Brown confirmed that he would not be signing the player as he did not think he would significantly improve the existing squad.
Thomas is the brother of VfB Stuttgart midfielder and German international Christian Gentner. In a 2010 interview with the German Football Association, Thomas accepted that he would be unlikely to ever play at the same level as his brother. In the same article, Christian claimed that Thomas has the potential and ability to succeed at Bundesliga II level.
- "Thomas Gentner profile (German)". weltfussballarchiv.com. Retrieved 4 July 2011.
- "Thomas Gentner statistics". soccerway.com. Retrieved 4 July 2011.
- "Thomas Gentner 2010–11 statistics". TuS Koblenz. Retrieved 4 July 2011.
- "TuS Koblenz and TSV Havelse start in Regionalliga (German)". Turus Sports Magazine. 2 July 2011. Retrieved 4 July 2011.
- "Offenbach Kickers look to new season (German)". Frankfurter Rundschau. 2 July 2011. Retrieved 4 July 2011.
- "Dons pre-season training camp – day one". Aberdeen F.C. 3 July 2011. Retrieved 4 July 2011.
- "German on trial with Aberdeen F.C.: Brown challenges Thomas Gentner". Evening Express. 4 July 2011. Retrieved 4 July 2011.
- "Match report: VfL Bochum 2–1 Aberdeen". Aberdeen F.C. 6 July 2011. Retrieved 6 July 2011.
- "Dons drop interest in trio". Eurosport. 7 July 2011. Retrieved 8 July 2011.
- "Narrow defeat in final pre-season friendly (Danish)". FC Nordsjælland. 9 July 2011. Retrieved 13 July 2011.
- "Gentner extends contract with Koblenz" (in German). Rhein Zeitung. 10 August 2011. Retrieved 11 August 2011.
- "Thomas Gentner: I am not my brother's clone (German)". German Football Association. 22 October 2010. Retrieved 29 June 2011.