Grigor Dimitrov's indifferent form continued with a third-round loss at the Miami Open, while Marin Cilic and Juan Martin del Potro moved into the last 16.
Dimitrov slumped to a straight-sets loss to Jeremy Chardy at the ATP 1000 event on Sunday, continuing a poor recent run.
The in-form Del Potro cruised past Kei Nishikori, while Cilic was pushed but also reached the fourth round.
Aside from Dimitrov's exit, it was a largely good day for the seeds.
DIMITROV DUMPED OUT
Dimitrov, the third seed, suffered a 6-4 6-4 loss to Chardy in just one hour, 25 minutes.
The Bulgarian had won his past three meetings with Chardy, but the Frenchman proved too good.
Dimitrov started the year well, making the semi-finals in Brisbane, last eight at the Australian Open and Rotterdam decider, but he has struggled since.
The 26-year-old has now lost four of his past five matches in a worrying run of form.
DEL POTRO, CILIC ADVANCE
Del Potro continued his form run with a 6-2 6-2 thrashing of Nishikori.
The Argentinian is on a 13-match winning streak after claiming titles in Acapulco and Indian Wells.
Cilic has been unable to find the same form since reaching the Australian Open final, but the Croatian second seed overcame Vasek Pospisil 7-5 7-6 (7-4).
STRONG DAY FOR SEEDS
There were six seeds advancing on Sunday.
Milos Raonic served 10 aces to get past Diego Schwartzman 7-6 (7-5) 6-3, while Filip Krajinovic will face Del Potro after beating Benoit Paire 6-3 6-3.
Chung Hyeon cruised past qualifier Michael Mmoh 6-1 6-1 and John Isner was untroubled by Mikhail Youzhny in a 6-4 6-3 win.