Allyson Felix, 30, is trying to make her fourth Olympic team at the U.S. track and field trials, which begin today in Eugene, Ore. (Jonathan Newton/The Washington Post)

When Allyson Felix lines up in the starting blocks Friday for her first race of the U.S. Olympic track and field trials, she will be surrounded by youth and promise. The lanes surrounding her include a 21-year-old from Fort Lauderdale, a senior at Tulane and a 21-year-old champion from the Pan American Games who was all of 9 years old when Felix first burst onto the Olympic stage.

Gearing up for the 400-meter preliminary heat, the 30-year-old Felix will be in Lane 4 with many miles behind her and, she hopes, at least a couple more Olympic titles ahead.

“It’s very weird,” said Felix, who has won six medals in three Olympic appearances. “I feel very old, especially when I hear the ages they were when they say there were watching [me].”

With a résumé already unmatched among American sprinters, Felix is in Eugene with history in her sights. She hopes to compete in a demanding double at the Rio Games — the 200 and 400 — and become the third woman to win gold in both at an Olympics.

But her road has become more challenging in recent months. What was supposed to be a career-defining year instead has been one beset by injury. In April, Felix was doing a core workout when she dropped from a pull-up bar and landed on a medicine ball, twisting her right ankle. She says she suffered significant tears in multiple ligaments, which kept her off the track for nearly a month.

“It was definitely a major setback, I would say. It’s been a really difficult year,” she said this week. “Things have definitely had to be altered a bit. . . . Definitely had to just kind of take a pause and kind of have a new plan to put things together. It’s been a very rocky road.”

Waiting for clearance to run, Felix instead focused on her physical therapy and rehabilitation. She worked in the pool and on an exercise bike. When she finally returned to the track in late May, she ran counter-clockwise, initially, which allowed her to push off on her left foot and protect the healing right ankle.

“I’ve never had a year like this. This is probably the most difficult injury I’ve faced just because of the time frame of everything,” she said.

More than two months later, the pain is still present, but Felix says she has come to Eugene prepared to qualify in both races. To earn a spot on the U.S. team, she will need a top-three finish in both. Track observers aren’t sure what to expect because Felix has been relatively absent from the running circuit this season. She skipped a Diamond League race in Doha, Qatar, and pulled out of the Prefontaine Classic in Eugene.

Since injuring her ankle, she has competed only once: a tuneup race in a small San Diego meet three weeks ago. She posted a 51.23 in the 400 there, well off her personal-best mark of 49.26 from Beijing last year, when she won the 400 world title.

“For me, I’m a fighter. It was going to take a whole lot not to get me here,” she said. “I’m going to give it everything I have.”

The women’s 400 heats begin Friday, and the final is scheduled for Sunday. The 200 event begins July 8.

Felix made an early splash in the sport by winning silver in the 200 at the 2004 Games. She was 18 years old at the time. Since then, in addition to four individual world titles, she has won three Olympic gold medals in relays, the 2012 Olympic title in the 200 and a silver in the same event at the Beijing Games. She has never won two individual medals at one Olympics — she competed in the 100 meters in 2012 and finished fifth — and has had her sights set on the 200-400 double for more than a year.

At last year’s world championships, the 200 and 400 races were scheduled about an hour apart, which forced Felix to choose between the two. The Rio Olympics initially stacked races into the same evening, but the sport’s governing body tweaked the schedule to allow Felix to chase history. If she can qualify in both events, the Rio schedule would call for her to race a 400-meter semifinal the evening of Aug. 14, followed by a 200 preliminary the next morning and the 400 final that night.

Before that, though, she knows she has to race through pain and earn her spot in Rio. The ankle injury hasn’t slowed her ambition.

“My goals are the same,” she said, “I want to make the team in both events. I’m going to leave it all on the track. I’m definitely optimistic. I think that’s just a part of who I am. This is something none of us saw coming, an obstacle in the road. That’s the thing about challenges: You get creative and figure out how to go through them.”

Note: Just one day before the men’s 800-meter preliminary heats, two-time Olympian Nick Symmonds was forced to withdraw from the Olympic trials because of a lingering ankle injury. Symmonds, 32, who finished fifth at the London Games and took second at the 2013 world championships, tweeted out a photo of his left ankle, saying, “This ankle has taken me to 2 Olympic Games, but it will not take me to a 3rd.”

An earlier version of this article indicated Felix would become the first woman to win gold in the 200 and 400. Two women have achieved that feat: American Valerie Brisco-Hooks in 1984 and Marie-Jose Perec of France in 1996.