In a testament to his tenacity, Hewitt became just the third active player to achieve the milestone, joining an elite group that includes two of the all-time greats, Roger Federer (937) and Rafa Nadal (674).
"Today was just like another match and an opportunity to go out there and play well," Hewitt told reporters. "Obviously afterwards, you know, a great milestone.
"Not many people get to achieve that. Not many people get the opportunity to get close to that, so it means I have been around for an awfully long time, as well.
"I'm getting old."
While Hewitt may have lost a step and his groundstrokes are not quite as ferocious, the 33-year-old has lost none of his combativeness, and it was on full display for a sun-kissed centre court.
After dropping the opening set and down a break 3-1 in the second, Hewitt, his trademark baseball cap turned backwards on his head, summoned his famous grit to sweep the next five games and level the match.
In the third, with Haase on the ropes, Hewitt delivered the knockout punch with another four-game run, sealing the match with a cheeky lob, a fist-pump and his hands raised in the air in triumph.
"I sort of had to weather the storm with him and in the end I found a way to be able to get through," said Hewitt. "The biggest turning point, I was struggling to break his serve.
"When I was able to get back on level terms in that break for 3-3 (in the second) that was a big momentum key for me."
An Australian Rules player growing up before focusing on tennis, Hewitt has brought the same rugged, take-no-prisoners approach of his nation's indigenous football game to the court for 16 years.
While Federer's style is often described as elegant and Nadal plays with controlled fury, Hewitt is a pure blue-collar brawler.
The fighting spirit and raw aggression has carried him to the top of the world rankings, 29 career titles, including Wimbledon and U.S. Open crowns.
"A few years ago when I had the last couple of surgeries I probably would have doubted I'd get to this stage anyway," Hewitt said in a moment of reflection.
"The tough times coming back from surgeries, that's motivation, it's only really my close group who know what we had to do to get back out here and compete again.
"The start of my career, the first three quarters I had no surgeries or big injuries at all. Then I had five surgeries in four years, and that sort of was tough to come back from.
"There were times when you doubted whether you were going to go out there and play again."
If Hewitt is to record win number 601 in Miami, he will have to be at his battling best against another player who brings plenty of fight to the court - Nadal.
A clash with the Spanish world number one is one he savours.
"I still play the game to have an opportunity to play against the best guys in the world and Rafa is," said Hewitt.
"No doubt about it, I look forward to the challenge.
"This is a really tough draw and frustrating, you don't get to have a crack at him later in the tournament."
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