Indian Wells champion Dominic Thiem's bid for a 'Sunshine Slam' met with a quick end as he fell 6-4 6-4 to Hubert Hurkacz in the Miami Open second round on Friday, while world number one Novak Djokovic wasted little time in dispatching Bernard Tomic.
The 22-year-old Hurkacz broke third seed Thiem four times, including in the final games of each set, to record the biggest win of his career.
Austrian Thiem, who beat Roger Federer on Sunday to win his first career Masters 1000 title at the BNP Paribas Open, was uncharacteristically sloppy.
Fifth seed Kei Nishikori was also sent packing from the second round after Serbian Dusan Lajovic stunned the Japanese world number six 2-6 6-2 6-3.
Next up for world No. 44 Lajovic, who had lost in the first round of five tour-level events this season, will be a clash with Nick Kyrgios after the Australian defeated qualifier Alexander Bublik of Kazakhstan 7-5 6-3.
Djokovic needed just over an hour to brush aside Australian Tomic 7-6(2) 6-2 and advance to the third round of a tournament he has won six times. The Serb improved his record to 6-0 against Tomic.
World No.1 Naomi Osaka of Japan endured a rollercoaster start to the Miami Open, advancing to the third round with a 6-0 6-7(3) 6-1 win over Belgian Yanina Wickmayer.
The Australian and US Open champion needed more than two hours to dispose of her Belgian opponent, having dispatched the 23-times grand slam singles champion 6-3 6-2 a year earlier.
Serena Williams regained her form after a shaky second set to dispatch Rebecca Peterson of Sweden 6-3 1-6 6-1 to set up a third-round clash with China's Wang Qiang.
It was the 10th-seeded American's first time on court since retiring during her third-round match at the BNP Paribas Open in Indian Wells with an illness earlier this month.
After a dramatic comeback win in her opening match, Canadian teen Bianca Andreescu took a more confident step towards the 'Sunshine Double', disposing of American 22nd seed Sofia Kenin 6-3 6-3 to reach the third round.