Career
He is a 2.08 m (6 ft 8 in) tall forward, who last played for KK Krka in Slovenian Telemach League. He played for Slovenia at the 2007 International Basketball Federation Europe Under-18 Championship. In 2013, Tratnik agreed a contract with KK Portorož, where he became the Most Valuable Player of the first week of the 2013-2014 Slovenian Basketball League, after scoring 25 points in the 92–70 away loss against KK Hopsi Polzela.
On Summer 2014 he signed with Zlatorog Laško, where he became two times Most Valuable Player of the week in the 2014-2015 Slovenian Basketball League.
On July 2015, Tratnik moved to KK Krka for debuting in the American Bar Association League. After regular season in American Bar Association League, on March 14, 2016, KK Krka and Tratnik terminated contact.
On March 18, 2016, KK Šentjur announced they had signed with Tratnik.