Daniil Medvedev took another step towards retaining a title for the first time in his career as the Russian third seed beat Germany's Dominik Koepfer 7-6(5) 6-0 on Tuesday to reach the Miami Open quarter-finals.
Medvedev overcame a shaky start and converted four break points while dropping serve just once to secure a spot in the last eight in Miami where he has yet to drop a set.
Koepfer was the early aggressor, using a pair of holds at love to build a 4-3 lead in the first set but Medvedev forced a tiebreak in which he lost the opening four points before finding his way.
With a frustrated Koepfer suddenly losing control of his forehand, Medvedev enjoyed much smoother passage through the second set where he broke twice to build a commanding 4-0 lead before closing out the match with a break to love.
"Sometimes it happens when you lose the first set the way he lost ... it brings your (opponent's) energy down and I knew that I had to use it (to my advantage) in the beginning of the second set that's where it was the most important," Medvedev said after collecting his 350th career win.
The Russian will face seventh seed Casper Ruud of Norway or Chile's Nicolas Jarry, the 22nd seed, in the last eight.
In other early action, unseeded Czech Tomas Machac beat Italy's Matteo Arnaldi 6-3 6-3 to reach his first Masters 1000 quarter-final.
Top seed Carlos Alcaraz, who beat Medvedev in the Indian Wells final nine days ago, will try to secure his passage to the last eight later on Tuesday when he meets Italian 23rd seed Lorenzo Musetti.
