Andy Murray lost to Russian top seed Daniil Medvedev at the Miami Open, as fellow Britons Dan Evans and Heather Watson were also beaten in Florida.
Medvedev, who must reach the semi-finals in Miami to reclaim the world number one ranking from Novak Djokovic, won the second-round match 6-4 6-2.
Evans was beaten in three sets by Japan’s Yoshihito Nishioka, who battled back to win 3-6 6-4 6-3.
Watson lost her third-round match to Switzerland’s Belinda Bencic 6-4 6-1.
Scotland’s Murray, 34, a two-time winner, has not won back-to-back matches since January.
The three-time Grand Slam winner, ranked 85th in the world, could not respond after being broken by Medvedev in the third game of the first set.
Medvedev lost the world number one ranking to 20-time Grand Slam winner Djokovic on Monday, having replaced the Serb as number one for three weeks.
The 26-year-old, who is not allowed to compete under his country’s flag following Russia’s invasion of Ukraine, saw out the match efficiently after breaking Murray’s serve for a 3-2 lead in the second set.
“My level of tennis is obviously not right now where it needs to be to win matches like that,” Murray said.
“Today there were some good signs on the court but the two key things in tennis are serve and return. I didn’t do either of them particularly well.”
World number 27 Evans made a promising start against Nishioka, ranked 96th, winning four straight games to close out the first set.
A break for 2-1 in the second set was enough to help Nishioka level the contest – and though Evans was able to restore parity at 2-2 in the deciding set, the increasingly frustrated Briton could not recover after being broken in the seventh game.
Watson, who claimed her first win over a top-20 player since 2020 by defeating Ukrainian Elina Svitolina in the previous round, was contesting a third-round match in Miami for the first time in six years.
The Briton had taken a 4-2 lead in the opening set but world number 28 Bencic responded emphatically, winning 10 of the following 11 games to reach the last 16.
Elsewhere on Saturday, Naomi Osaka advanced to the last 16 with a walkover after Czech player Karolina Muchova withdrew because of injury.
The United States’ Australian Open finalist Danielle Collins, seeded ninth, beat Russian Vera Zvonareva 6-1 6-4, while Belarusian 12th seed Victoria Azarenka overcame Russian Ekaterina Alexandrova 6-4 2-6 7-6 (7-5).
In the men’s draw, Norwegian sixth seed Casper Ruud progressed with a 6-1 6-2 win over Switzerland’s Henri Laaksonen, but Canadian seventh seed Felix Auger-Aliassime lost to 22-year-old Serb Miomir Kecmanovic 6-4 6-2.
Polish eighth seed Hubert Hurkacz,the defending champion, defeated France’s Arthur Rinderknech 7-6 (7-5) 6-2, and Spanish 15th seed Roberto Bautista Agut beat Poland’s Kamil Majchrzak 6-3 6-3.