Britain's Andy Lapthorne was beaten in the NEC Wheelchair Tennis Masters quad singles final as Australian Dylan Alcott won 3-6 7-5 6-4 in Florida.
Alcott, 27, beat Lapthorne to win 2016 Paralympic gold and again in the 2017 Australian Open final.
Lapthorne, 28, beat world number one David Wagner and Koji Sugeno in Orlando during the week but suffered a fourth Masters final defeat.
Alcott moves top of the world quad rankings, with Lapthorne up to second.
"This sport is so hard," Lapthorne said. "I've tried so hard and I keep putting myself out there and it's just not meant to be right now.