Laura Robson failed to make it a second British success in Miami as she and partner Lisa Raymond were defeated 6-1 7-6 (7-2) in Sony Open women's doubles final.
Earlier on Sunday, US Open winner Andy Murray climbed to number two above Roger Federer in the world rankings following his epic three-set success over David Ferrer.
However, Robson and veteran American Raymond, who at 39 is two decades older than the young Brit, were unable to beat Russia's Nadia Petrova and Slovenia's Katarina Srebotnik.
The match was over inside an hour and 10 minutes, with the victorious pair converting five from 10 break points.
Raymond, who has won 11 Grand Slam doubles titles, has been impressed by the young Brit in the past week, 'Team Robmond' - as they have been calling themselves - having only been formed two days before the start of the tournament.
Raymond had been due to play with Sam Stosur but the Australian had to pull out with a calf injury.
In the semi-finals they beat the world number one pair of Sara Errani and Roberta Vinci, and Raymond hopes they will team up again in the future.
"Laura has an unbelievable future in front of her," Raymond said. "We're definitely planning on, you know, hooking up and playing more.
"I just need to talk to some of the people that I was supposed to be playing with possibly. I think it's a partnership that can only get better.
"I think the more time you spend together on the practice court or just, you know, on the match court - and it's been great with Laura."