Stan Wawrinka is braced for more "painful" defeats after losing to qualifier Donald Young and Benoit Paire had a huge meltdown as he also suffered a first-round exit in the Citi Open.
Wawrinka has endured an almighty struggle this season following a second knee operation and went down 6-4 6-7 (5-7) 7-6 (7-3) to Young in Washington on Tuesday.
The three-time grand slam champion, who has taken a wildcard for qualifying for the Rogers Cup in Toronto, knows he will have to be patient following his latest early exit.
Wawrinka, down in 198th in the rankings, said: "It's a tough loss that's for sure. It's painful to lose first round here, especially 7-6 in the third,
"I was missing a lot, not feeling the way I wanted. I'm looking for confidence. It's tough to not win a lot of matches so then you start to think too much on the court."
The Swiss added: "You need to accept it's going to be painful. I've been there before and it took me a lot of time, a lot of years to win grand slams so I'm okay to take a few more months to try to push me and come back."
Paire took his frustration out on his rackets as Marcos Baghdatis consigned him to a 6-3 3-6 6-2 loss.
The fiery Frenchman smashed one racket into the hard court after netting an overhead volley, then destroyed another when he got back to his chair, which he booted in frustration, and hurled down a third racket when Baghdatis put him out of his misery.
Top seed and defending champion Alexander Zverev won the first set against Malek Jaziri 6-2 before rain halted his second-round match.
Jared Donaldson, James Duckworth, Denis Kudla, Daniil Medvedev and Alex de Minaur all made it into round two.