Roger Federer saw off American teenager Frances Tiafoe in his first match at the Miami Open for three years.
The Swiss, 35, beat the 19-year-old qualifier 7-6 (7-2) 6-3 to take his 2017 record to 14 wins and one defeat.
Federer, who won has won the Australian Open and Indian Wells titles this year, missed Miami through illness in 2016.
Top seed Stan Wawrinka beat Horacio Zeballos 6-3 6-4, and women's sixth seed Garbine Muguruza defeated Zhang Shuai 4-6 6-2 6-2.
In the men's doubles, fourth seeds Jamie Murray and Bruno Soares beat Treat Huey and Max Mirnyi 6-4 6-3.