Americans John Isner and Ryan Harrison were round winners at the $1.155 million Regions Morgan Keegan Championships on Tuesday.

Isner, the tournament's top seed, defeated Gilles Muller 7-6 (7-1), 7-6 (7-4) on the indoor hardcourts at The Racquet Club of Memphis. He was the runner-up here to fellow American Sam Querrey two years ago and fired 26 aces to dispatch Muller in 1 hour, 40 minutes.

Harrison, a native of Shreveport, Louisiana, downed Jack Sock 6-3, 2-6, 6-4 in Tuesday's nightcap.

Meanwhile, a wild card Querrey smacked 12 aces before overcoming Colombian Alejandro Falla 2-6, 6-3, 6-4, Ryan Sweeting pasted fellow American James Blake 6-0, 6-2 in a mere 44 minutes, and Ukrainian Sergiy Stakhovsky defeated American qualifier Robert Kendrick 6-3, 7-6 (8-6). The former top-five star Blake was a runner-up here back in 2002.

The 2012 Memphis champ will pocket $277,915.