Top seed Dominic Thiem eased into the third round of the Citi Open and he was joined by Kei Nishikori and Juan Martin del Potro.
The rain, which washed out the remainder of the WTA schedule on Tuesday, did not dampen Thiem in his first ATP 500 outing as a top seed after he accounted for Henri Laaksonen 6-3 6-3.
Thiem - who lost in the fourth round at Wimbledon - dropped just one point on his first serve and did not face a break point throughout the second-round clash in Washington.
Nishikori, the second seed, was tested before getting past Donald Young 6-3 4-6 7-6 (7-5).
The Japanese star, champion in 2015, squandered eight break points in the third set, but eventually claimed a hard-fought win.
Argentinean Del Potro - a three-time winner of the event - saw off Lukas Lacko 7-5 6-2.
Champion in 2008-09 and 2013, Del Potro fired down 15 aces and won 84 per cent of his first serves against the Slovak.
American eighth seed Jack Sock progressed to the last 16 of the Citi Open for a third successive year following his 7-6 (7-2) 7-6 (8-6) victory against Marius Copil, while Mischa Zverev went down 6-7 (5-7) 7-6 (7-2) 6-3 to Guido Pella.
In other results on Tuesday, Marcos Baghdatis beat Edan Leshem 7-6 (7-1) 6-0, Kyle Edmund was too good for Chung Hyeon 6-3 6-1, Go Soeda lost 7-6 (7-2) 6-3 to Tennys Sandgren, Malek Jaziri prevailed 7-5 7-5 over Alessandro Bega, Jordan Thompson defeated Ruben Bemelmans 6-3 6-2, while Dmitry Tursunov outlasted Mitchell Krueger 6-4 6-7 (4-7) 6-4.