Roger Federer took his 2017 record to 15 wins from 16 matches as he beat Juan Martin del Potro at the Miami Open.
The Swiss, 35, won 6-3 6-4 in 55 minutes to reach the last 16, where he will face Spanish 14th seed Roberto Bautista Agut.
Czech 10th seed Tomas Berdych beat Luxembourg's Gilles Muller 6-3 6-4 and goes on to play Frenchman Adrian Mannarino.
Swiss top seed Stan Wawrinka takes on Tunisian Malek Jaziri later on Monday.