World number two Andy Murray was dumped out of the Miami Open by Grigor Dimitrov in three sets.
Murray prevailed in a first-set tie-break and looked destined to reach the last 16 until Dimitrov rallied to see off the 2013 champion 6-7 (1-7) 6-4 6-3 on Monday.
Awaiting 26th seed Dimitrov is Gael Monfils, who downed Pablo Cuevas.
Japanese sixth seed Kei Nishikori booked his spot in the fourth round via a routine victory against Alexandr Dolgopolov.
Roberto Bautista Agut outlasted ninth seed Jo-Wilfried Tsonga in three sets, while Milos Raonic and Nick Kyrgios accounted for Jack Sock and Tim Smyczek respectively.
MURRAY FADES AS DIMITROV RALLIES
Dimitrov had lost six of the previous eight meetings between the pair, but came from behind at the ATP 1000 event.
Murray had appeared on track to continue his dominance, only to give up a 3-1 lead in the third set.
It marked a second-straight third-round exit for Murray, who finished with 50 unforced errors, since he went down to Novak Djokovic in the Australian Open final.
The duo traded early breaks before Murray won 11 of 13 points to finish the first set, only for a poor start to the second to see him fall behind.
That allowed Dimitrov to level the match, but Murray made the better start to the third set by breaking for 3-1.
However, Dimitrov fought back again and Murray sent a backhand long to fall 4-3 behind as he lost five straight games.
OVERDUE WIN FOR BULGARIAN, NISHIKORI CONTINUES FINE MIAMI FORM
Dimitrov's victory against Murray was his first against a top-10 player since May 2015, when he defeated Stan Wawrinka in Madrid.
Nishikori advanced to the fourth round of the tournament for a fifth successive year.
Monfils fired down 13 aces and did not face a break point in his 6-3 6-4 win over Cuevas.
DIMITROV HAPPY, MURRAY BEMOANS MISTAKES
"I just played better in the big moments today," Dimitrov said. "I had quite a few opportunities and I used them."
After tallying 22 unforced errors in the third set alone, Murray lamented: "In the third set, he managed to get up a break and then I made a lot of unforced errors. Credit to him. He was more solid than me."
"Everything worked well," Nishikori said. "Not many easy mistakes and I served well today, so that was the key."
QUARTERS ON THE LINE FOR DJOKOVIC AND CO.
Two-time defending champion Novak Djokovic will meet 14th seed Dominic Thiem for a quarter-final berth on Tuesday. Nishikori will back up against Bautista Agut, while seventh seed Tomas Berdych takes on Richard Gasquet.