Andy Murray won the US Open in 2012Andy Murray's preparation for this month's US Open began with a first-round defeat at the Washington Open.
The 35-year-old lost 7-6 (10-8) 4-6 6-1 to Sweden's 115th-ranked Mikael Ymer.
Of his chances of being seeded for the US Open, the former world number one and current number 50 said: "It's still possible, but I'll need to certainly play better than I did."
There were wins for Kyle Edmund and Jack Draper, but Katie Boulter was defeated in the Silicon Valley Classic.
Boulter shocked eight seed Karolina Pliskova by storming to the first set, only for the Czech to come through 1-6 7-6 6-3.
Edmund beat Japan's Yosuke Watanuki 6-4 7-6 (10-8) on his return to the ATP singles after a 20-month layoff to set up a meeting with compatriot Dan Evans,
Edmund has had three left knee surgeries and was playing in his first tour-level singles match since October 2020.
He said: "I didn't find it easy. I hung in there and I got my reward in the end."
Draper beat American Stefan Kozlov 7-5 6-2 to progress and will now face Russia's Andrey Rublev.
Harriet Dart also lost in Washington, with China's Zhu Lin winning 6-4 6-3, while Emma Raducanu's professional doubles debut - alongside Denmark's Clara Tauson - ended in a 6-4 6-1 loss to Romanian Monica Niculescu and Czech Lucie Hradecka.
Seven-time Grand Slam champion Venus Williams, playing her first singles match in nearly a year, was also eliminated in the opening round in Washington, falling to Canadian qualifier Rebecca Marino 4-6 6-1 6-4.
"It was nice to have the crowd behind me," said the 42-year-old. "Definitely a great experience - just trying to shake off some rust. That's just to be expected."
Meanwhile, Kazakhstan's reigning Wimbledon champion Elena Rybakina lost 1-6 6-2 6-0 to seventh seed Daria Kasatkina at the WTA San Jose hardcourt tournament.
