Katie Ledecky celebrates winning the 400-meter freestyle in a world-record time of 3:58.86 at USA Swimming Nationals in Irvine, Calif. She matched former great Janet Evans by holding world marks in the 400, 800 and 1,500 freestyle concurrently. (Harry How/Getty Images)

Katie Ledecky says she’s not competitive outside of the pool, other than the occasional game of Scrabble with her older brother, Michael. Funny, because it’s hard to imagine her any other way.

Ledecky, 17, set her third world record of the year at USA Swimming Nationals on Saturday night in Irvine, Calif., winning the women’s 400-meter freestyle in 3 minutes 58.86 seconds. She crushed a record set by Italy’s Francesca Pelligrini, who held the previous mark of 3:59.15, which she set in 2009 — the height of the tech-suit era, when swimmers wore polyurethane suits crafted in NASA wind tunnels.

Ledecky, who won her first gold medal at 15 and a year later set her first and second world records, has now matched American distance star Janet Evans by holding world marks in the 400, 800 and 1,500 freestyle events concurrently.

“Honestly I didn’t think about it too much,” Ledecky said. “It was on my mind, but I didn’t let it overtake me today, and I think that’s something that definitely helped. I was very relaxed.”

That’s been her style since making her first nationals appearance at the 2012 Olympic trials.

Evans held all three records from 1988 to 2006.

“It means a lot. It’s an honor to be mentioned in the same sentence as Janet,” Ledecky said. “She’s a great person and a really great role model for all U.S. distance swimmers.”

Ledecky’s time in the 400 on Saturday night was the fourth under the four-minute barrier — three of which belong to Ledecky.

Ledecky was under world record pace the entire race and at one point pushed it to 1.71 seconds under. She faded slightly in the final lap, but it didn’t matter with so few yards to go. The record was already gone.

“It was probably pretty close to perfect,” Ledecky said.

When she lifted her head to the brightly lit timing board, Ledecky cheered wildly, splashing the water and smiling broadly to the crowd where her family, including Michael, sat watching.

It was Ledecky’s third of an expected four wins at the meet, having already claimed the 200 and 800 freestyle. On Sunday, she will swim the 1,500 freestyle, an event in which she’s the No. 1 seed by more than 30 seconds.

If she completes the 200 through mile sweep, she’ll earn the chance to swim all four events at the Aug. 21-25 Pan Pacific Championships in Australia.

Cierra Runge finished second in 4:04.67, and Leah Smith was third at 4:06.28.

Ledecky’s Nation’s Capital Swim Club teammates Isabella Rongione, 14, and Megan Byrnes, 15, finished sixth and seventh in the “C” final.

Michael McBroom won the men’s 400 free in 3:47.19 and was in the ready room awaiting his final when Ledecky electrified the crowd.

“We were talking in there, ‘Oh man, she might beat some of us,’ ” he said. She didn’t.

Sterling native Matt McLean finished second in 3:47.30. It was his second podium finish after winning the 200 freestyle Thursday.

Less than an hour later, Michael Phelps finished in a disappointing sixth place in the men’s 100 backstroke. Olympic champion Matt Grevers won in 52.75.

Jack Conger, three-time All-Met Swimmer of the Year, finished 10th.

Missy Franklin picked up her second win of the week with a victory in the women’s backstroke (59.38).

Micah Lawrence tied Jessca Hardy in the 100 breaststroke, with both touching in 1:06.51.

Cody Miller and Nic Fink pulled a surprise upset of American record holder Kevin Cordes in the men’s event. Miller had the only sub-minute time to win in 59.91. Georgetown Prep’s Carsten Vissering finished third in the “B” final followed by Langley grad Chuck Katis in fourth.