(CNN) -- Andy Murray is still waiting for his first title of the year after wasting a match point before going down in three sets to Sam Querrey of the United States in the final of the ATP tournament in Los Angeles.
The top seed had his chance in the 10th game of the second set on Querrey's service but sent his backhand wide.
Querrey, who had never beaten Murray in four previous meetings, went on to take the second set on a tiebreaker and broke the Scot in the sixth game of the decider.
The hometown player served for the match at 5-3 and faced a break back point before closing out victory 5-7 7-6 6-3 after Murray sent a backhand long.
Querrey has now claimed four titles this season, one shy of world number one Rafael Nadal, who has taken five.
"In the second and third sets I played great, some of the best tennis I've played," Querrey told the official ATP Tour website.
"That's the highest-ranked guy I've ever beaten."
For world number four Murray it is another frustrating defeat after taking up a late invite from organizers to play in California after world number two Novak Djokovic pulled out.
"I've got to be happy getting to the final and having chances to win," Murray said. "I didn't play my best tennis. Just tired."
Murray is playing without a coach after splitting from Miles Maclagan earlier this week and looking for a replacement ahead of the U.S. Open later this month.
His year started with much promise, but after losing in the final of the Australian Open to Roger Federer, the 23-year-old has struggled to find his best form.
Querrey is the first player to win the Farmers Classic tournament in successive years since Andre Agassi in 2002.