Grigor Dimitrov fell in the Citi Open second round after a surprise straight-sets loss to Daniel Evans in Washington on Tuesday.
Bulgarian 12th seed Dimitrov, who has endured a below-par year, went down 6-4 6-4 to Brit Evans at the ATP 500 event played on hard courts.
Dimitrov won more return points but was broken four times to make an early exit.
No other seeds fell as Benoit Paire, Sam Querrey and Alexandr Dolgopolov advanced to the third round.
Paire had the fewest problems, brushing past Jared Donaldson 6-0 7-5, while Querrey overcame Bjorn Fratangelo 6-7 (5-7) 6-4 6-4.
Dolgopolov, the 2012 champion, was pushed by Jordan Thompson before edging the Australian 6-4 1-6 7-6 (7-4).
Qualifier Ryan Harrison came through his opener, sending down nine aces in a 7-6 (7-1) 6-3 win over Stephane Robert.
Ernesto Escobedo had no such luck in the first round, going down to Donald Young 6-4 3-6 6-3, while Sam Groth served 18 aces but suffered a 7-6 (7-3) 7-6 (7-5) loss to Brian Baker.
Teenage wildcards Denis Shapovalov and Reilly Opelka were unable to make the most of their chances.
Opelka went close before losing to Malek Jaziri 6-7 (4-7) 7-6 (7-4) 7-6 (7-3), while Shapovalov suffered a 7-6 (7-3) 4-6 6-4 loss to Lukas Lacko.
Lu Yen-hsun beat Austin Krajicek 6-1 7-6 (7-3), while Yoshihito Nishioka led Ivan Dodig 6-2 4-2 when the Croatian retired due to the heat.
Steve Johnson led Adrian Mannarino 4-2 when play was suspended due to storms.