Mardy Fish will play Andy Murray in the second round of the Cincinnati Masters after claiming his first ATP Tour singles victory since 2013.

The 33-year-old American, who has revealed he will retire following the US Open, missed 18 months of tennis due to a heart condition, but he looked more than comfortable when dispatching world No.20 Viktor Troicki 6-2, 6-2 in just 68 minutes.

Fish told atpworldtour.com: "I was a little surprised at my level. I hadn't practised a ton or particularly well for a little while. I was struggling with my serve.

"A friend of mine came in a couple days and helped, but it was still sort of a struggle even yesterday to sort of find my serve.

"I was obviously real happy with the level."

Next up is the newly-promoted world number two and recent Rogers Cup winner Murray.

"He's pretty fantastic so far," Fish said of the in-form Scot. "He's won a ton of matches. He's won more matches than anyone this year, so he'll be tough."

Ivo Karlovic is through to a second-round meeting with Martin Klizan after beating 10th seed Gilles Simon 6-4, 6-7 (3/7), 6-2 while Thomaz Bellucci edged Jiri Vesely 7-6 (7/5), 6-2 to book a clash with Tomas Berdych.

Benoit Paire's prize for conquering Gilles Muller 7-6 (7/5), 7-6 (8/6) is a showdown with top seed and world number one Novak Djokovic and Marin Cilic lies in wait for Joao Sousa after the Portuguese removed Philipp Kohlschreiber with a 6-2, 6-7 (5/7), 6-2 victory.

Gael Monfils fell at the first hurdle, the 14th-seeded Frenchman going down 6-4, 7-5 to Jerzy Janowicz, while Andreas Seppi defeated his fellow Italian Adrian Mannarino 6-3, 6-3 and Bernard Tomic downed Sergiy Stakhovsky 6-4, 6-3 to progress.

Also victorious on Monday were Vasek Pospisil, David Goffin, Roberto Bautista Agut, Jack Sock and Thanasi Kokkinakis.

In the women's competition, Venus Williams resisted a spirited performance from Zarina Diyas to triumph 7-6 (8/6), 6-4 – she will next face Ana Ivanovic.

Wimbledon finalist Garbine Muguraza made an early exit thanks to Yaroslava Shvedova, who beat the ninth seed 6-4, 7-6 (7/0), while Timea Bacsinszky was another seed to exit early as Madison Keys pulled off a 6-4 6-3 win.

Qualifier Timea Babos shocked Sam Stosur to progress as a 7-4 (8/6), 4-6, 7-5 victor, Jelena Jankovic recovered to beat Madison Brengle 4-6, 6-4 6-2, Coco Vandeweghe dominated Yulia Putintseva 6-3, 6-2 and Karin Knapp toppled Ana Konjuh 7-5, 6-1.

Andrea Petkovic downed her fellow German Julia Goerges 6-4, 6-2 and there were three-set wins for both Tsvetana Pironkova and Varvara Lepchenko.

The last matches to finish saw 14th seed Elina Svitolina recover from a wobble to beat Alison Riske 6-2, 4-6, 6-0 and Irina-Camelia Begu needed an hour and a half to knock Alize Cornet out of contention with a 6-4, 6-4 win.