Bulgarian Grigor Dimitrov got off to a good start at the Nitto ATP Finals Monday with a victory over Dominic Thiem of Austria.

In a topsy-turvy duel between two swashbucklers with single-handed backhands, Bulgarian Grigor Dimitrov earned his first win at the Nitto ATP Finals with a hard-fought victory over Austrian Dominic Thiem Monday afternoon in London.

The 26-year-old Dimitrov is playing in his first year-end event after a season that saw him win the biggest title of his career in Cincinnati and have arguably his best run in a major when he pushed Rafael Nadal to five sets in Melbourne.

Both players came out of the gates playing well and produced some wonderful tennis early on.

But it was Thiem who blinked first as he was broken at 2-3 to hand Dimitrov an advantage that he would not relinquish en route to closing out the set 6-3.

Despite currently sitting at a career high ranking of world number 4, the 24-year-old Austrian has struggled for most of the second half of 2017. After starting strong and having an elite clay court season, Thiem has not advanced past the fourth round of any tournament since Roland Garros.

But Thiem appeared to gain more confidence as Monday’s match progressed into the second set. His first serve percentage improved and he saved a key break point in the 11 th game with a trademark massive forehand winner.

The Austrian would go on to break the Bulgarian in the very next game to earn the second set 7-5 and force a decider.

Dimitrov once again reasserted himself in early stages of the third and earned two break point opportunities in the sixth game; however, Thiem steeled himself and saved both. Undaunted, the Bulgarian reapplied the pressure immediately in his next return game and this time came up with the goods on break point.

But the match had more twists and turns to come as Dimitrov was unable to serve out the match at 5-4. Thiem broke back, but was subsequently broken again in the very next game. After nearly two-and-a-half hours, Dimitrov earned match point and Thiem shanked a backhand long to end the encounter.

Group play is set to continue at the Nitto ATP Finals Monday evening when world number 1 Rafael Nadal will take on David Goffin.