Nick Kyrgios stuns Andrey Rublev at Miami Open but hit with Indian Wells fine

Nick Kyrgios has thrashed world number seven Andrey Rublev in straight sets at the Miami Open, but has received a fine for his on-court behaviour at last week's Indian Wells tournament.

The Australian was fined $US25,000 ($33,000) by the ATP for nearly hitting a ball kid after smashing his racquet and yelling an audible obscenity during his Indian Wells loss to Rafael Nadal on March 18 AEDT.

He was fined $US20,000 for unsportsmanlike conduct and $US5,000 for the audible obscenity.

In Miami, Kyrgios needed just 51 minutes to defeat Rublev 6-3, 6-0 in their second-round match.

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

But it was all downhill from that point for the Russian, as 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 beat Japan's Taro Daniel 6-7 (7-1), 6-2, 7-6 (7-5) earlier in the day.

Among other matches, world number four Alexander Zverev's superior serving led to a 6-4, 3-6, 6-3 win over Borna Coric.

Zverev served his way out of trouble in the first game of the third set and fended off a break point while serving up