Australian wildcard Nick Kyrgios needed 51 minutes to stun world number seven Andrey Rublev of Russia 6-3, 6-0 and German Alexander Zverev's superior serving led to a 6-4, 3-6, 6-3 win over Borna Coric of Croatia in second round action at the Miami Open on Friday.

Rublev looked good at the start, building a 2-1 lead after breaking Kyrgios in the early stages of the first set.

But Kyrgios piled up the winners and put pressure on Rublev's serve by stepping into the court to take the ball early.

"I don't think I played unbelievable, I just played the right way," Kyrgios told Tennis Channel. "Against Rublev, you know he wants to try and dictate, to have a lot of rhythm, and I didn't give him that today. I tried to slap as many winners as I could, serve well and get up the court on my return and it worked."

Kyrgios, who has won five of his last six matches, will next play Italian Fabio Fognini, who defeated Japan's Taro Daniel earlier in the day.

Zverev, having split the first two sets against Coric, served his way out of trouble in the first game of the third set and fended off a breakpoint while serving up 5-3 en route to the hard-fought win.

The German, who fired down 12 aces and only committed one double fault, said his more aggressive approach was the difference in the contest.

"The last few matches I was losing close three-set matches because I felt I wasn't going for it," said Zverev, who fell to Tommy Paul in a tight three-setter in the second round of Indian Wells earlier this month.

"Today I felt like if I'm going to lose, I'm going to go for it. That worked out and hopefully it will in the next match as well," he added. 

American Coco Gauff defeated China's Wang Qiang 7-5, 6-4 in their women's singles match on Friday. In the next round-of-32 match, 18-year-old Gauff will take on another Chinese player, Zhang Shuai, who routed Sorana Cirstea of Romania 6-1, 6-1 in only 53 minutes.

Linda Fruhvirtova of Czech Republic produced a career-best performance on Friday to stun Elise Mertens of Belgium.

The 16-year-old Czech player, who arrived in Florida with a ranking of 279, upset 24th seed Mertens 7-5, 2-6, 6-1 in her first contest against a top-50 player.

(With input from agencies)