Top seed and defending champion John Isner beat qualifier Sergei Bubka of the Ukraine 7-6 (3), 4-6, 6-3 in the opening round of the Hall of Fame Tennis Championships on Tuesday.
The 11th-ranked Isner relied on his overpowering serve despite playing lethargically at times.
Second-seeded Kei Nishikori, Japan's top player and the highest ranked player ever from his country - at No. 18 - also won his opening match, defeating Igor Sijsling from The Netherlands 6-4, 6-4.
Isner is slated to face Nicolas Mahut in the second round match. The pair met in the longest match in tennis history â€” 11 hours, 5 minutes before Isner's 70-68 fifth-set victory in 2010 at Wimbledon.