Kumantsov, who won a total of 16 Futures titles, made the main draw of two ATP Tour tournaments, both times as a qualifier. At the 2011 Open 13 in Marseille he was beaten in the first round by Nicolas Mahut, then at the 2012 St. Petersburg Open he retired hurt in his opening round match against Jürgen Zopp, when only one game away from losing, citing dizziness.