Paula Radcliffe suffered her first individual loss in more than 30 months when she was beaten over 10km at an international meeting in Puerto Rico.
Radcliffe is gearing her season towards winning Olympic gold
Running her first race of the year, she finished second to Kenyan-born Dutch athlete Lornah Kiplagat.
"I felt flat. I don't like being beaten but it's not a disaster in these conditions," said the Briton.
Radcliffe, who finished four seconds behind Kiplagat, was going for a third successive victory in the race.
She added: "I'm not that far off what I've run here in the past. And Lorna
ran very, very well. I'm not off course."
Kiplagat won in a time of 30 minutes 41 seconds.
Last year, Radcliffe clocked 30:21 to win the event and set a new world 10km road race record in the process.
Radcliffe will now return to her training base in the mountains of Albuquerque, New Mexico, to prepare for the world cross-country championships in Brussels on 20 March.