Before she was tall, before her interviews were polished, before she became one of the fastest women in the world and poised to be a breakout star of the Tokyo Olympics at 19 years old, Athing Mu got some advice from her coach.

“You can either be the rabbit, or you can be the fox,” Bernice Mitchell told 9-year-old Athing one day as she was working out, as usual, with the boys at the Trenton Track Club in New Jersey.

“Establish what you are as soon as you step up to the starting line, and do not waver,” Mitchell recalled during a recent interview. “If you decide to be the fox, then go eat. If you decide to be the rabbit, don’t get eaten.”

A decade later, this past June 28, Mu — whose full name is pronounced “uh-THING moe” — started off intending to be the rabbit at the U.S. Olympic trials 800-meter finals. But as she came off the first turn and moved to the inside lane, Mu was clipped on one foot from behind. She stumbled badly and found herself in third place, running in an outside lane.

Mu played the fox for half a lap, moved into the lead at the bell, then bolted through the final turn and crushed the rest of the field by 10 meters to win in 1:56.07. It was the fastest time in the world this year — and if she had been challenged down the home stretch, Mu clearly could have run faster.

“Sometimes I know I’m breaking a record, but the majority of the time, you’re just running and trying to get to the line,” Mu said in a radio interview a week later. “With my 1:56, I didn’t know I was going that fast. I just didn’t want to get caught.”

“She didn’t lose focus when she got hit, she didn’t panic,” Mitchell said. “She just started eating, eating, eating. And then that last 50, it was like, come get me if you can.”

Mu was born in Trenton, New Jersey, to immigrants from Sudan. One year ago, she arrived on the Texas A&M campus as a freshman with a high school personal best of 2:01. Under the guidance of head coach Pat Henry and assistant coach Milton Mallard, she set new collegiate indoor and outdoor records in the 800 (1:57.73), 400 (49.57) and 4×400 relay (3:22.34). She gave up her remaining eligibility and turned pro before trials, signing with Nike for an estimated $500,000-$750,000 per year before performance bonuses.

“For her to step down and run that fast or 400 meters is truly unbelievable,” said Henry, who also coached 2019 world 800-meter world champion Donovan Brazier. But what’s even more remarkable about Mu, he said, is her character, poise, faith, and humility.

“I’ve had thousands of athletes,” said Henry, who has been coaching for 48 years and won 36 NCAA team championships. “When these Olympics are over, I think that she is a young lady that not just by her performance, but by her presence and by her personality and her expressions when somebody puts a microphone in her face, I think people are going to see a young lady that we’re extremely proud of as Americans that she’s representing our country.”

As the fifth of seven children, and the first of her siblings to be born in the United States, Mu followed her older siblings to the Trenton Track Club. Mitchell and head coach King Jennings quickly recognized her talent, and they charted a course for her that avoided burnout, having her practice only two days per week. With natural speed, she competed in all the sprints as well as the 800. But one day when Mu was about 9, after finishing a 100-meter dash, she broke down in tears in the cool-down area.

“What’s wrong, Little Mo?” Mitchell asked.

“It’s too short,” she cried. “The race is too short.”

After middle school, Mu began working out more frequently. She did not run for her high school team, where the best athletes are often asked to compete at numerous distances in the same meet. She focused on the 400 and 800, but Mitchell, who also teaches in the Trenton school district, advised Mu to choose one race and “own it — make it yours.”

They spent countless hours traveling to meets and talking about how Mu should present herself for interviews and conduct herself on social media. They critiqued recordings of interviews and practiced talking to the mirror.

The result is who is headed to Tokyo: a confident, intelligent 5-foot-11 young woman with a dazzling smile and all the speed in the world.

“Her consistency is what makes her special,” Mallard said. “She knows how to compete, she doesn’t get rattled with competition. She’s level-headed and always focused mentally. That’s what separates her from a lot of good athletes, to make her great, is her focus.”

Before Mu’s big races, Mitchell likes to write what she believes will be Mu’s wining time on a note card. She did it before the trials. Now the card for the Olympic finals is tucked under her TV cable box, ready to be run into existence. Mitchell won’t reveal what her prediction for is, but “she’s faster now than she was at the Olympic trials.”

She may need to be. Caster Semenya, the two-time defending Olympic champion, is not allowed to compete in Tokyo after she refused to regulate her naturally occurring high testosterone level.

But five other women have run under 1:57 this year: Rose Mary Almanza of Cuba, Natoya Goule of Jamaica, Workua Getachew of Ethiopia, and Great Britain’s Laura Muir and Jemma Reekie. No American woman has won the Olympic 800 since Madeline Manning in 1968. The 800 is often very tactical, with lots of bumping and jostling. There’s no telling whether Mu will need to be the rabbit or the fox.

If the trials are any guide, Mu can win either way.