Venus Williams served up plenty of history-making game this US Open.

The 45-year-old athlete entered the tournament as the most senior competitor in the past 40 years and spent much of her three weeks on the court outperforming opponents who were only half her age.

The key to coaching such a prominent athlete? Allowing her to lead, yet knowing when to advise her to rest, according to her coach, Diego Ayala, who spoke to The Post.

“When dealing with a player of Venus’s caliber and background, it’s crucial to understand what she needs from a coach and align with those expectations,” explained Ayala, 46, a professional trainer from Florida.

Although they’ve only partnered since June, under Ayala’s guidance, Williams became the second-oldest player to secure a WTA Tour-level victory in July.

When she competed at the US Open last month, she set a record as the oldest singles player there since 1981, only surpassed by Renee Richards, who was 47 back then.

At 45, Williams is nearly double the age of her competitors — studies indicate that the average age of top players is between 25 and 28.

That means her training might look a little light compared to the average player.

Williams spends up to three hours a day on the court between drills and scrimmaging — and a heavier emphasis on recovery.

“At times, I’d have to suggest, ‘Let’s ease up today. You’ve pushed hard for four consecutive days!’ I needed to dial her back a bit,” he mentioned.

Ayala claimed there was no “secret sauce” to leading Williams to her success, but indicated that the strong relationship they built together was a major asset.

The pair came up in the tennis world at the same time — though Williams and her sister, Serena, were mega stars who “transcended the sport.”

“At first, it was kind of strange, but at the same time, I think it helped us bond a little bit better and understand each other because we are from the same era. We got a lot of the same jokes and same perspective,” Ayala said.

“If you know your stuff and she recognizes it, then she’s gonna ask for more, and so once she started asking me for more, then I’m going to give her as much as I can of myself,” he continued.

“She has the mentality, she can improve everything, all the time. So I would tap into that and help her improve the things that she already knew she wanted to do. That’s kind of how our relationship worked, and it really clicked.”

When it came to Williams’ loss Tuesday, Ayala said she was taking it well — and that the pair left “no regrets” on the court.

“One of her goals was — especially for the Open — was to enjoy herself, to embrace the challenge and the competition. And she did that with a smile on her face. So that was awesome to see,” Ayala said.