Halep defeated by Agnieszka Radwanska in three sets on Saturday.
World No 1 Simona Halep beaten in Miami as Caroline Wozniacki complains of fan behaviour
World No 1 Simona Halep tumbled out of the Miami Open on Saturday, falling 3-6, 6-2, 6-3 to Poland's Agnieszka Radwanska.
The third-round defeat comes a week after Romania's Halep was toppled in the semi-finals at Indian Wells by Japan's Naomi Osaka, who went on to win the title in the California desert.
With the first set in hand, the mercurial Halep was clearly frustrated when Radwanska dropped just four points in the opening four games of the second to seize a 4-0 lead.
Halep reclaimed one break, but was broken again as Radwanska forced a third set, in which an early break put Halep up 2-0.
The Romanian couldn't maintain the advantage, however, and her 44 unforced errors were too much to overcome as Radwanska won six of the last seven games to seal the victory.
Radwanska, the 2012 Miami champion, hadn't posted back-to-back match victories since January.
She next faces former world No 1 Victoria Azarenka, who rallied for a 3-6, 6-4, 6-1 victory over 20th-seeded Latvian Anastasija Sevastova.
Azarenka, of Belarus, is unseeded this year as she tries to get her career back on track after taking time off to have a baby.
Despite the defeat, Halep is assured of retaining the number one spot when the rankings are updated at the end of the tournament.
But her exit leaves the women's field in the elite hardcourt tournament without its top two seeds after second-seeded Australian Open champion Caroline Wozniacki lost to Monica Puig on Friday night.
Wozniacki was smarting Saturday, not from anything Puig offered on court but from what she said was threatening and vulgar behavior by fans at the match.
In a Twitter post, the Danish star called on Miami Open organizers to act after fans threatened her parents and swore at the niece and nephew of her fiance, David Lee.
Tournament director James Blake said player security was the event's "No. 1 priority".
"During the match, we had tournament and WTA staff, as well as tournament security courtside," Blake said in a statement. "They never witnessed, nor were they notified of any specific threats made to the players or their families. If they had been notified, the situation would have been handled immediately."