ATP World Tour Masters 1000 gets underway on Sunday
The American hit 20 aces and saved both break points to improve to 3-4 against Troicki in their FedEx ATP Head2Head series. Isner, who is 9-1 in his past 10 matches, has won two titles in the past month: the Dell Technologies Hall of Fame Open in Newport and the BB&T Atlanta Open.
He reached the Cincinnati final in 2013, beating Novak Djokovic and Juan Martin del Potro before falling to Rafael Nadal in the final. Isner will next meet a compatriot, either #NextGenATP Tommy Paul or Donald Young.
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Gilles Muller, also a two-time titlist this season, leaned on his serve to get through a tight first-round contest against Ryan Harrison of the U.S. Muller struck 21 aces in a 6-4, 5-7, 7-6(3) win that took two hours and four minutes.
Muller, the 16th seed, is making only his second appearance in Cincinnati. He fell in the first round in 2015 to Benoit Paire. The Luxembourg left-hander will next play Albert Ramos-Vinolas of Spain or Russian Mikhail Youzhny.