Former British number one Laura Robson's latest comeback from injury ended in a 6-3 1-6 6-3 loss to 17-year-old American Ingrid Neel in Florida.
The 21-year-old, ranked 557th in the world, was playing in the qualifying round for the ITF event, which has a total prize fund of £17,500.
Robson has had niggling injuries since having wrist surgery in 2014 and had 18 months out of the game.
She reached a career-high singles ranking of 27 in July 2013.
Robson returned at Eastbourne last June after her wrist operation, but played only 10 singles matches in 2015, and was knocked out of both Wimbledon and the US Open in the first rounds.
She played her last match of the year in September, taking the rest of the year off to continue her recovery.
"Little niggles have cropped up as they do when you are not using your body in the way that you want to on the match court," said Britain's Fed Cup captain Judy Murray.
"I can only imagine it must be hugely, hugely frustrating but the key for her is to make sure her body is absolutely ready to go, however long that takes."