Stefan Kozlov mainly plays on the ATP Challenger Tour and the ITF Future Tour . So far, he has won a doubles title on the Future Tour alongside Sekou Bangoura . On the Challenger Tour he has so far won two titles in double competitions and two individual titles. In 2013 he was in the main draw of an ATP World Tour tournament for the first time when he received a wildcard in Newport . However, he failed in three sets to Michał Przysiężny . His first participation in a Grand Slam tournament was in 2014 in the doubles competition at the US Open , where he also received a wildcard alongside Noah Rubin .