Serena Williams attended the premiere of the EPIX original documentary “Serena” earlier this month in New York. (Andy Kropa/Invision/Associated Press)

For those outside Serena Williams’s inner circle, her unparalleled success — especially when combined with her powerful game and occasionally brusque public persona — makes it perhaps easy to believe that the biggest star in women’s tennis is somehow impervious to the oft-staggering pressure.

Never were the impossibly high standards placed upon Williams more readily apparent than last season: The world No. 1 was not merely expected to win the first Grand Slam since Steffi Graf in 1988; she was destined to dominate at every junction along that historic track.

But that Grand Slam failed to materialize, even as Williams recorded a season for the ages. That year and its resulting heartbreak are in focus in “Serena,” a new feature-length documentary set to air Wednesday at 8 p.m. on EPIX.

Heading into next week’s Wimbledon, the timing of the film feels particularly appropriate. The 34-year-old Williams has lost in two straight major finals, further emphasizing the historic and improbable nature of her incredible 2015 season, one in which she finished with a 53-3 record and added three major titles to her collection before falling in the U.S. Open semifinals.

“Serena” takes viewers behind the scenes during that season, while revealing a side of Williams that isn’t often apparent.

From the French Open to right after the U.S. Open, director Ryan White was granted access to Williams and her close-knit group, which includes Coach Patrick Mouratoglou, agent Jill Smoller, hitting partner Robbye Poole and her sisters. As part of White’s discussion with Williams before filming began, he chose to shoot the documentary cinema verite style (i.e. fly on the wall) with a very minimalist, non-invasive crew.

“It’s not a biopic,” White said late last month in a phone interview from Los Angeles. “It’s not a recap of Serena’s career. What I hope is for tennis fans and non-tennis fans alike that it is a front row seat, like an all-access pass to the on-the-road, in-the-life for a year with one of the greatest champions of all time in any sport.”

A tennis fan and former junior player, White, 34, had admired Williams from afar and was slightly intimidated at the thought of meeting one of the biggest names in all of sports when he was first introduced to the star in Paris last year shortly before the French Open. Thus, one can imagine his relief in discovering Williams is a lot more easygoing than her public persona has revealed.

It’s a theme White successfully establishes from the very beginning of the film.

“She’s so laid back and I expected much more of a fierce personality off the court,” White said, “and perhaps some diva behavior.”

The director attempts to contrast Williams’s on-court persona with shots of how the player spends her down time: singing, dancing and organizing her own fashion show.

Perhaps no scene depicts that laid back off-court demeanor more than what follows Williams’s triumph at the French Open. Williams is shown celebrating her victory at Roland Garros by eating Chinese food and watching “The Little Mermaid” on her laptop.

The film also explores Williams’s close familial ties, naturally focusing on the training that she and her sister, Venus, received from their father, Richard, while growing up in Compton, Calif.

“He’s the reason we even play tennis,” Williams says in the film. “[Venus and I] both have new coaches now that we’re in our 30s, but whenever I’m heading into Grand Slams, it’s the lessons from my dad that I remember.”

On camera, Williams also repeatedly says that she did not feel any pressure during the year — an assertion she made again during a news conference after her U.S. Open loss — though it’s evident from the film that the attention surrounding the Grand Slam had an effect on her.

In a poignant scene, Williams is visibly annoyed while passing a New York City billboard of herself before the U.S. Open.

“I don’t care if I win, lose or draw,” she says while riding in a car. “I’m ready to get this done, started and over with. And what happens, happens. And I’m not even going to feel any pressure. I just want to get it over with. I don’t want anyone to talk about me. … I have nothing to lose. It’s not going to change my career. It’s not going to change my path. If I don’t win this, it’s not going to be the end of the world.”

What happens next is, of course, well documented: Williams is shocked in the semifinals by Italy’s Roberta Vinci and fails to win the Grand Slam. Williams’s team has trouble getting in touch with her afterward. It was a few days later that Williams tells White that the loss put her “in a really dark hole” and that she felt she “let a lot of people down.”

The film then cuts to footage of Williams as a child and then to Williams giving a speech after being named Sports Illustrated’s Sportsperson of the Year, a crowning moment in one of the most remarkable tennis seasons in history.

“I think it was very brave of her,” White said of the year-long filming process. “I think it exposes a lot of vulnerable parts of your life if you know someone with a camera is going to be there in the ups and downs. I definitely give her a lot of credit for that.”