Hewitt's assessment comes as the United Cup draw announcement confirmed de Minaur's preparation for the home slam will include a chance to avenge last month's US Open loss to Englishman Jack Draper.
The hip injury that forced de Minaur to withdraw from his Wimbledon quarterfinal match with Novak Djokavic flared up against Draper in the same stage of the US Open.
The injury remains a talking point as the curtain begins to close on a de Minaur's breakthrough year, during which he entered the top 10 in the ATP rankings for the first time.
The Australian world No.9 suffered a shock quarterfinal loss to Hugo Gaston at the European Open last week but is back on court from Tuesday (AEDT) at the Vienna Open, with the Paris Masters looming beyond that.
Jack Draper will take on Alex de Minaur in the United Cup after beating the Aussie at the US Open. (Matt Turner/AAP PHOTOS)
"He's really just trying to build up the matches now," Hewitt said on Monday.
"I don't think he was really prepared to play that tournament (the European Open), it was just kind of trying to get some cobwebs out and actually play a couple of matches before he goes into playing a 500 this week."
But de Minaur's availability for the Davis Cup finals remains under a cloud, and may depend whether he qualifies for the ATP Finals in Turin - a prospect that took a heavy hit bowing out of the European Open early.
"He's still giving himself a chance for Turin and obviously the Davis Cup Finals if he's up for it," said Davis Cup captain Hewitt.
"A lot depends over the next month."
Despite the injury disrupting the end of de Minaur's year, Hewitt is hopeful it will be in the past by the summer, and remains sure that 2025 marks the Sydneysider's best chance of finally making it beyond the round of 16 at Melbourne Park.
"Absolutely," he said.
Lleyton Hewitt is hoping Alex de Minaur can at least make the quarterfinals at the Australian Open. (Lukas Coch/AAP PHOTOS)
"The highest you get seeded, it takes out some of the dangerous players at the top of the game and you sometimes get a kinder draw.
"He certainly wants to push deeper. He's only done the round of 16 at the Australian Open and the last three majors after that this year have been quarterfinals.
"Fingers crossed he can tick that off and at least make the final eight.
"He's really just added layers to his game (this year).
"He's been able to build a little bit more strength as well so he's got a bit more firepower, but we know how well he moves around the court."
Australian captain Hewitt joked at the United Cup draw announcement on Monday that de Minaur would be filthy at facing a British team set to include both Draper and the Australian's girlfriend Katie Boulter.
"You're in trouble, you're in so much trouble," he grinned to Casey Dellacqua after she drew Great Britain into Group F of the mixed team tournament that begins in December.
"We had to play against Katie last year and I think that was the one and only time they were prepared to do it."
Australia has drawn Great Britain and a yet to be decided third team for the United Cup in December. (Bianca De Marchi/AAP PHOTOS)
The third team in Australia's group will be decided by combined WTA and ATP rankings at the end of the season, but is likely to be either Croatia or Argentina.
American world No.4 Coco Gauff looms as the biggest drawcard as Perth hosts Groups A, C and E, while Poland's Iga Swiatek and Norwegian Casper Ruud are among the big names across groups B, D and F converging on Sydney.
UNITED CUP GROUPS:
Group A - US, Canada, TBC
Group B - Poland, Czech Republic, Norway
Group C - Greece, Kazakhstan, Spain
Group D - Italy, France, Switzerland
Group E - China, Germany, Brazil
Group F - Britain, Australia, TBC
