EUGENE, Ore. (AP) — Allyson Felix's dalliance with the 400 meters has led to a dilemma of whether she will run the event at worlds or hand off the spot to a teammate.

That decision could take days, maybe even weeks, to reach.

Felix needed just 50.19 seconds — along with a powerful kick and a lean at the finish — to edge Natasha Hastings on a scorching Saturday at the U.S. championships.

The schedule at worlds is just too tight for Felix to consider racing the 400 along with the 200, which is her signature event and one she doesn't have to run at nationals because she already has an automatic bye in the event to Beijing later this summer.

Hanging in the balance is Francena McCorory, who had the fastest time in the world heading into the race, but struggled around the track and finished fourth. The top three qualify.

Should Felix not run the 400 at worlds, McCorory would likely take her place.

"I would hope to get a decision pretty quickly, just to let the next person know," Felix said.

This was a difficult event to earn a spot, so much so that Olympic gold medalist Sanya Richards-Ross didn't even qualify for the final. Felix was behind most of the way Saturday before turning it on with the finish line in sight.

"I just buckled down and went for it," Felix explained.

That describes Justin Gatlin's speedy race, too. He really didn't mean to run this fast, either.

His legs just took over.

Gatlin exerted little energy in his first race at nationals, easily winning his opening heat of the 200 with a blazing time.

The 33-year-old sprinter finished in 19.92 seconds on a steamy afternoon. According to USA Track and Field, it's the fourth-fastest time in the first round of a 200.

After the race, sprinter Curtis Mitchell cracked: "Hey, Gat. Slow down, bro!" Wallace Spearmon also greeted Gatlin with, "Why so fast?" Gatlin just grinned and responded: "I didn't know what I was running."

The polarizing sprinter with a doping past was feeling particularly fresh after skipping the 100 because he has an automatic bye to worlds from his 2014 Diamond League title.

"My coach said to take it easy through the rounds," Gatlin said.

Gatlin didn't listen, of course. The only sprinters to run a 200 prelim faster are Carl Lewis (19.84), Shawn Crawford (19.88) and Michael Johnson (19.89).

Isiah Young had the second-fastest time of the afternoon, finishing 0.07 seconds behind Gatlin. The sprinters train together in Florida.

Amped up before the race, Gatlin was raring to go. He was a spectator Friday night when Tyson Gay cruised to the win in the 100. Gatlin thinks if he would've been racing, he might have run 9.6 seconds on the super-fast Hayward Field track. That sort of time would've beaten Gay — who's not running the 200 — and broken Gay's American record of 9.69 set in 2009.

That's all conjecture, though. A little brash, too.

"The 100, that's what I've been working on, steadily but surely," Gatlin said.

There's a certain sprinter some 3,000 miles from Eugene surely taking notice — or about to anyway. Usain Bolt, the world record-holder in the 100 and 200, isn't running this week at the Jamaican nationals, taking the opportunity to hone his technique since he already has automatic byes into both events being the world champion.

Gatlin can't fault Bolt for squeezing in some extra work.

"Why go out there and feel the pressure from young guys trying to beat you, trying to get their confidence up?" said Gatlin, who served a four-year ban after testing positive for excessive testosterone in 2006. "Go home, train, get ready for Beijing and come out like a champion."

Other things to know from Saturday:

DAWN'S DAY: Dawn Harper-Nelson got off to a fast start and cruised to the 100 hurdles title. Lolo Jones hit two hurdles and didn't finish the race.

PICKING UP THE PACE: Matthew Centrowitz had one goal entering the 1,500 final — dominate. He did, too, finishing in 3:37.25 to win by more than a second. "Going into the home stretch, I wanted the race to be won already," Centrowitz said. "Think I did that."

OF MERRITT: David Verburg caught world champion LaShawn Merritt down the stretch to win the men's 400. "I wasn't expecting it," Verburg said.

QUITE A LEAP: Tianna Bartoletta took the long jump title with a world-leading leap of 23 feet, 4 1/2 inches. She narrowly missed earning a spot in the 100 the day before.

ESTEEMED COMPANY: 400 hurdler Bershawn Jackson captured his fifth outdoor title, joining Arky Erwin and Edwin Moses as the only ones to win that many in the event.

MORE TITLES: Teenager Vashti Cunningham, the daughter of longtime NFL quarterback Randall Cunningham, won the junior national high jump title Saturday by clearing 6-0 1/2. Her older brother, Randall, captured the men's junior national crown in the event the day before.