Entertainment

Double serving

Showtime’s upcoming documenetary, “Venus and Serena,” finally offers an explanation for why 31-year-old Serena Williams — the world’s No. 1 female tennis player and likely the greatest female player of all time — is so hard to defeat.

Turns out that when she’s on the court, she has several people — in her head — backing her up.

“I definitely have different personas,” Williams says in the doc, describing personalities within her that are so distinct they have their own names.

“There’s Summer. She helps me out a lot. Like, if I have to write long letters,” says Williams. “[Then] there’s Tequanda. Tequanda is rough. She is not Christian. She’s from the ’hood. She was at the US Open in 2009.”

Williams is referring to an incident at that year’s US Open semi-finals when she went off on a line judge after a critical foot fault call. “I’ll f—ing take this ball and shove it down your f—ing throat . . . You better be f—ing glad that I don’t do that,” she yelled at the woman.

Serena refers to this as a “match that Tequanda played,” then says, “I wasn’t there, but I heard about it . . . ”

According to veteran documentary filmmaker Maiken Baird, who co-directed “Venus and Serena” with TV news producer Michelle Major, Serena’s distinct personalities are both complex and very real.

“Serena has these multiple personalities that she uses to cope with life,” says Baird, who, with Major, filmed the sisters for 10 months in 2011. “Some people really compartmentalize their lives, and Serena is one of them,” she says. “She’s got that real mean streak that makes her so great, and then she’s got this really sweet side.”

Also featured in the doc is Richard Williams, Venus and Serena’s father. Despite residing in the hardly tennis-friendly city of Compton, Calif., Richard decided before his daughters were born that they would become tennis professionals. (Venus, 33, also holds 7 Grand Slam singles titles.)

When the girls were young, Richard would go to private country clubs to ask for their used tennis balls and developed an extensive training regimen that had the girls throwing baseballs, footballs, and even their tennis racquets in order to improve their power.

Oddly, “Venus and Serena” — premiering Aug. 23 — found itself enmeshed in a controversy, when The United States Tennis Association (USTA) sued the filmmakers for copyright infringement, claiming they failed to sign an agreement giving them rights to use footage from previous US Opens (primarily the ’09 Serena outburst footage). The filmmakers responded that they have the right to use the footage under fair use laws, and the suit is ongoing.

(The USTA did not respond to a request for comment.)

In the end, Baird hopes that despite the controversy, people will feel an intimate bond with the sisters. “What we were trying to get to was how they really are as people — their humanity,” he says.