Kyle Edmund squandered three match points in his first-round defeat to Jared Donaldson, becoming the fourth British player to exit the tournament at the first hurdle.
The world number 45 lost 6-2 6-7(4) 2-6 to join Dan Evans, Aljaz Bedene and Heather Watson in dropping out on a dismal Wednesday for the British contingent in Florida.
Edmund started well enough, holding his serve throughout the opener and earning two breaks to take a comfortable lead in the match, getting over the line with his third set point.
The second set proved to be a tight affair, but Edmund did enough to edge 5-3 ahead and had three match points to book a place in the next round, only for Donaldson - 95th in the world - to recover and force a tie-break.
From that point on momentum swung in the American's favour, as he took the tie 7-4 and then held in the deciding set to set up a meeting with Mischa Zverev in the last 64.
World number one Andy Murray is not competing in Miami due to injury, leaving seeded Johanna Konta as the last Brit standing in either of the singles draws.