Juan Monaco of Argentina reached the quarterfinals in his Malaysian Open debut but fellow seeds Alexandr Dolgopolov of Ukraine and Feliciano Lopez of Spain couldn't join him on Thursday.
No. 2 Monaco began his chase for a fourth title this year by beating Taiwanese wild card Jimmy Wang 6-4, 7-5. The Argentine responded to losing his serve three times by breaking Wang five times.
Dolgopolov, the No. 4 seed who also had a first-round bye, lost to Alejandro Falla of Colombia 6-3, 3-6, 6-3.
''I started really bad and missed a lot of balls,'' Dolgopolov said. ''I came back in the second set but it was an up and down match.''
Falla's second quarterfinal of the year will be against Julien Benneteau of France.
Dutchman Igor Sijsling served up only his sixth win of the year with a second-round upset of No. 5 Lopez, 7-6 (0), 7-6 (2). They played impeccably on serve with 11 aces each and no break points conceded, but Lopez crumbled in both tiebreaks.