WHAT HAPPENED: In the nightcap in Louis Armstrong Stadium, No. 28 Kevin Anderson fought off a dogged Paolo Lorenzi to reach his second US Open quarterfinal, 6-4, 6-3, 6-7, 6-4.

It was a match devoid of rhythm, just as the South African likes it, until midway through set three, when Lorenzi began to challenge the Anderson serve with surprising regularity. Lorenzi was able to engage the 6-foot-8 Anderson in punishing rallies throughout the latter two sets, but the No. 28 seed managed to regroup from a break down in the fourth to advance.

The Italian matched the lanky bomber hold for hold in the first nine games, and the story of the early going was Anderson's inability to capitalize on a buffet of second serves. Lorenzi's 43 percent first-serve percentage was offset by Anderson's poor returning, until a break in an eventful 10th game ended the set.

Lorenzi fired two timely aces to turn 30-40 into Ad-in, but a pair of double faults handed Anderson a second set point, which he converted with a forehand winner.

One break is usually enough for Anderson, and in set two, it came with Lorenzi serving at 2-3. The South African reeled off four straight points after falling behind 0-30. Just as in set one, he was aided by a Lorenzi double, one of his nine in the match.

"I imposed my game early on," said Anderson of his gameplan. "But he is a terrific fighter. He never gives in, and he fights for everything."

After holding with ease in his first 12 service games, it was unlucky 13 for Ander son in set three. A determined Lorenzi stung his opponent with a passing shot on his first break point of the match, coolly handling a second-serve serve-and-volley charge.

It was the first time the towering Anderson was broken in the tournament, ending a perfect run of 55 consecutive holds, the longest streak of any man in the field.

But Anderson snapped back immediately, grinding his way through a handful of uncharacteristically long rallies to get back on serve at 3-4.

The point of the match came with Lorenzi serving at 5-5, 15-30. In the 29-ball rally – the longest of the match – Lorenzi displayed tremendous defense, twice scampering far beyond the tramlines before baiting Anderson into a backhand unforced error.

The Italian would ride the momentum to take the set, 7-4, in the tiebreak, and he continued to make the Anderson serve look mortal early in the fourth. After threatening in his first return game of the set, Lorenzi secured his second break of the match when an Anderson double fault handed the Italian a 3-2 advantage.

Anderson later attributed the change in dynamic to a drop in temperature as the match carried on into the evening: "It felt much cooler. The balls became much softer and slower... I felt like he had a little bit more time to get some of the returns back in play." 

But yet again, Anderson responded with an immediate break back. Suddenly, the South African was looking at three virtual match points, at 3-4, 0-40 on the Lorenzi serve. In another twist, the Italian ran off five points in a row (including a 13-shot rally in which he needed to about-face at net to track down an Anderson lob) to level the set at 4-4.

After a quick hold, Anderson again created a 0-40 opening, and three match points with it in his next return game. This time, he made no mistake, closing the match out in two hours, 56 minutes in front of a crowd that swelled as the match tightened.

"The crowd was fantastic," he smiled after the victory. "That's why I love coming back here."

WHAT IT MEANS: The South African dispelled the demons of a 1-9 career record in Grand Slam fourth rounds to match his career-best major result, a 2015 quarterfinal appearance here in New York. In that run, he beat No. 3 Andy Murray in Round 4 before losing to No. 5 Stan Wawrinka.

He improves his lifetime record against Lorenzi to 4-0, and 2-0 both this year (Geneva) and in majors (2013 Australian Open).

The victory sets up a quarterfinal date with the winner of Sam Querrey and Mischa Zverev, who will close out the night session in Arthur Ashe Stadium. In this wide-open bottom half of the men's draw, No. 17 Querrey is the only man to have reached a Slam semifinal.

MATCH POINT: Opportunity knocks for Anderson. Can he answer the call and reach his first Grand Slam semifinal?