He had 11 double-faults and 53 unforced errors Tuesday.
On the women's side, fourth-seeded Sara Errani posted a "double bagel," beating Olivia Rogowska 6-0, 6-0 in 51 minutes. The 151st-ranked Australian was a "lucky loser," falling in qualifying but making the main draw when Ayumi Morita withdrew because of injury.
Seventh-seeded Petra Kvitova weathered another tough U.S. Open match, needing three sets and nearly two hours to beat 92nd-ranked Misaki Doi. Kvitova won 6-2, 3-6, 6-1 on a windy day at Arthur Ashe Stadium.
Kvitova has reached at least the semifinals at the other three major events; she has never made it past the fourth round at Flushing Meadows.
"I like big matches on the big stadium, but the people — it's too much crowds for myself, I think," she said.
She's also struggled in the North American swing leading to the U.S. Open, but she made a breakthrough last year. Kvitova won two of those tournaments and reached the semifinals at another in 2012, then matched her longest run at the year's last Grand Slam tournament.
The final set Tuesday was closer than the score in this rare matchup of two lefties. After Kvitova went up a break at 2-0, Doi had a chance to break right back but couldn't convert.
Two years ago, Kvitova became the first reigning Wimbledon women's champion to lose her first U.S. Open match in the same season. She was in danger of another early exit Tuesday when she made 15 unforced errors in the second set.
But she's hardly fazed by three-set matches. Kvitova recently played six straight across three tournaments, winning four of them.
Doi, from Japan, fell to 0-4 against top 10 opponents.
Players in action later Tuesday include top-seeded Novak Djokovic and two-time Australian Open champion Victoria Azarenka.