Novak Djokovic cruised past Lorenzo Musetti 6-2 6-2 to reach the quarter-finals of the Miami Open.

The match was delayed because of rain and world number five Djokovic, who has won six Miami titles, started slowly and was broken in the opening game as Italy's Musetti opened up a 2-0 lead.

But Serbian Djokovic, 37, completely dominated the match from that point.

The 24-time Grand Slam champion won nine consecutive games, closing out the first set 6-2 and moving 3-0 up in the second.

"It was tough, particularly in the first seven, eight games of the match," said fourth seed Djokovic.

World number 16 Musetti, 23, offered little resistance after winning those opening games as Djokovic cruised through to set up a tie with American Sebastian Korda.

Korda booked his place in the quarter-finals earlier on Tuesday with a 6-4 2-6 6-4 victory over Frenchman Gael Monfils, while Argentina's Francisco Cerundolo is also through after beating Norway's Casper Ruud 6-4 6-2.

Watching Djokovic from the grandstands was 23-time Grand Slam champion and former women's world number one Serena Williams.

He produced a backhand winner for a 5-2 second-set lead and sealed the win when Musetti double-faulted on match point.

"Actually, when I had that down-the-line passing shot, I pointed to her and asked her whether it was OK," said Djokovic.

"She said, 'yeah, it was fine'. If Serena says it was fine, then it was amazing by everyone else's standards."

In the women's draw, world number one Aryna Sabalenka reached the semi-finals in Miami for the first time by defeating China's Zheng Qinwen 6-2 7-5.

Sabalenka, who beat ninth seed Zheng in the Australian Open final in January, battled back from 4-2 down in the second set to seal a victory.

The 26-year-old Belarusian will face Jasmine Paolini in the last four, after the Italian sixth seed secured a 6-3 6-2 win over Magda Linette.

Paolini saved seven of the eight break points she faced during her quarter-final match against Poland's Linette.

After extending her head-to-head record against Zheng to 6-0, Sabalenka said she was "really proud" of the way she handled her emotions.

"Even when something didn't work well, I was there and I was fighting for every point," she added.