Top-seeded American John Isner and fourth- round winners at the $1.155 million Regions Morgan Keegan Championships on Thursday.

Isner, who was this tournament's runner-up to Sam Querrey in 2010, dispatched fellow American Donald Young 7-6 (7-3), 6-4 on the indoor hardcourts at The Racquet Club of Memphis.

Raonic, who lost to Andy Roddick in last year's Memphis finale and is fresh off his title in San Jose last week, got past Ukranian Sergiy Stakhovsky 6-4, 6-4.

Third-seeded Czech Radek Stepanek was also a winner on Thursday. The 2009 Memphis runner up ousted American Ryan Sweeting 4-6, 6-3, 7-6 (7-4) in 2 hours, 21 minutes.

Querrey, meanwhile, took down seventh-seeded Russian Kevin Anderson 7-6 (7-4), 6-4.

Additionally on Thursday, Austrian Jurgen Melzer bested Croat Ivan Dodig 2-6, 6-3, 7-6 (7-5), Olivier Rochus, of Belgium, beat Yankee Ryan Harrison 6-4, 7-5, Lukasz Kubot, of Poland, ousted German Philipp Petzschner 7-6 (7-5), 6-2 and German Benjamin Becker took down Xavier Malisse, of Belgium, 7-6 (7-4), 6-4.

The 2012 Memphis champ will pocket $277,915.