Memphis, TN (SportsNetwork.com) - Towering Croat Ivo Karlovic was a first- round victor Tuesday at the Memphis Open tennis event.

The 6-foot-10 fifth seed from Croatia smashed 23 aces in getting past Slovak Lukas Lacko 7-6 (9-7), 6-3 at The Racquet Club of Memphis. Karlovic was last year's Memphis runner-up here to Japanese star Kei Nishikori.

Also on Day 2, American qualifier Ryan Harrison topped Tunisia's Malek Jaziri 7-6 (7-3), 7-6 (7-1); American Denis Kudla vanquished Aussie fellow qualifier Thanasi Kokkinakis 6-3, 6-4; American qualifier Austin Krajicek outlasted Kazakhstan's Mikhail Kukushkin 6-2, 6-7 (3-7), 7-6 (10-8); and Aussie Bernard Tomic overcame Dutchman Igor Sijsling 4-6, 6-3, 6-2.

This week's top seeds are the U.S. Open runner-up and two-time defending Memphis champ Nishikori, Kevin Anderson and former Memphis runner-up John Isner. Nishikori will face Harrison in the round of 16.

The 2015 Memphis champ will earn $106,565.