Top seed Daniil Medvedev was too good for Frances Tiafoe, while Stefanos Tsitsipas is in the hunt for his first ATP Masters title.
Stefanos Tsitsipas and Andrey Rublev reached the last 16, however, in-form seed Aslan Karatsev farewelled Miami.
Daniil Medvedev could barely walk but still progressed from the third round on Sunday.
Greek star Stefanos Tsitsipas and Kei Nishikori will meet in the third round of the Miami Open.
Last week's Mexican Open champion Alexander Zverev went down in the second round in Miami to Finland's Emil Ruusuvuori.
Lorenzo Musetti reached last week's Mexican Open semi-finals and started at the Miami Open with victory.
Vasek Pospisil took aim at the ATP chairman as he lost in three sets to Mackenzie McDonald in Miami.
Another injury setback for the former world number one has delayed his first Masters 1000 appearance since 2016.
Almost two years on since his last appearance on the ATP Tour, Juan Martin del Potro needs another knee procedure but will not give up.
Alexander Zverev topped Stefanos Tsitsipas to reign supreme at the ATP 500 tournament on Saturday.