(Photo credit: Mike Frey-Imagn Images)

The roof was figuratively caving in on two-time defending Australian Open champion Jannik Sinner before he received help from above -- literally.

Thanks in large part to a mid-match roof closure at Rod Laver Arena in Melbourne, Sinner got past the United States' Eliot Spizzirri 4-6, 6-3, 6-4, 6-4 on Saturday to reach the fourth round of the Australian Open.

Trailing Spizzirri in the third set and experiencing debilitating cramps in his arms and legs, Sinner rallied after play was suspended for about 10 minutes and the roof was closed due to sweltering conditions.

When play resumed, Sinner broke Spizzirri to get the set back on serve, and the Italian went on to prevail.

The suspension was prompted by the tournament's extreme heat policy. When the chair umpire made the announcement, Spizzirri was up 3-1 in the third set. The players left the court, and the roof was shut.

'I struggled a bit physically,' Sinner said after closing out the win. 'I got lucky with the heat rule, when they closed the roof, I took my time. As time passed, I felt better and better.'

'It started with the leg, then it got into the arms, so I was cramping a bit all over, but this is the sport.'

Sinner was one of three seeded Italian players who earned wins in the Saturday heat.

Fifth-seeded Lorenzo Musetti went the distance against Tomas Machac of the Czech Republic and prevailed 5-7, 6-4, 6-2, 5-7, 6-2 in a match that took 4 hours, 27 minutes. The majority of the contest was played in scorching conditions, but the roof was closed early in the deciding set.

Musetti, who leads the strong Italian contingent in Melbourne, has reached the fourth round of the Australian Open for the first time.

Machac captured the fourth set with an apparent momentum-gaining break of serve. But Musetti responded, breaking his opponent at love to open the deciding set. Machac steadied himself and stayed within 3-2, but the Italian only lost three points in the final three games to advance.

Musetti will face the winner of the match between ninth-seeded Taylor Fritz and the 2014 champion, Switzerland's Stan Wawrinka. Earlier this week, Wawrinka, 40, became the second-oldest man to win a match at the Australian Open.

Musetti's countryman, 22nd-ranked Luciano Darderi, was able to get through his match at Kia Arena and pulled off a minor upset of No. 15 Russian Karen Khachanov. Darderi prevailed 7-6 (5), 3-6, 6-3, 6-4 to advance to the fourth round of a major championship for the first time in his brief career.

Darderi, who won 27 of his 32 first-service points in the last two sets, next will face off with Sinner.

--Field Level Media