Kozlov was the Spaniard’s practice partner on Monday when he was called up as a last-minute replacement for injured Frenchman Maxime Cressy in the main draw.
Apart from a brief stint in the second set, when he took advantage of his only breakpoint opportunity in the match, Kozlov was no match for Nadal whose previous best start of 11–0 in 2014 ended with a defeat to Switzerland’s Stan Wawrinka in the final. of the Australian Open.
Next up for the 35-year-old will be another American 39th-ranked Tommy Paul with a potential semifinal clash against top-seeded Russian Daniil Medvedev, whom he defeated in the Australian Open final by two sets.
“It is always important to win as soon as possible, but the most important thing is to win,” said Nadal after his victory in an hour and 16 minutes in hot and humid conditions.
“Tonight it was straight sets, that’s good news and I’m going to try to be ready again tomorrow against a tough opponent.”
Medvedev previously crushed Pablo Andújar 6-1 6-2 and pushed himself three wins from the tournament victory and rose to the world number one for the first time.
Medvedev pretended to serve underhand at match point, but instead hit his seventh ace, evoking a smile from the 68th-ranked Spaniard who played well but couldn’t break down the Russian’s solid defense.
Medvedev then takes on Japanese qualifier Yoshihito Nishioka and a title on Sunday for the Russian guarantees his rise to the world rankings as a replacement for Serbian Novak Djokovic.
The world’s number four, Stefanos Tsitsipas, also wasted little time piloting American qualifier JJ Wolf, the French Open finalist who sprinted to a 6-1 6-0 victory in just 47 minutes in the final game of the evening on the main field.
It was the 23-year-old Greek’s fastest win in his career and he will next face the 59th American Marcos Giron, who previously defeated Spaniard Pablo Carreño Busta 6-7(7) 6-4 7-6(4), for a place in the semifinals.