The United States Olympic gymnastics trials begin on Thursday with Jade Carey having accomplished something seven-times national champion Simone Biles has not - clinched her spot on the team for the Tokyo Games.

Taking advantage of a revamped qualifying system, Carey secured her Tokyo place with a string of strong results at four World Cup competitions through 2018 and 2019, leaving a packed talented field to fight over five remaining berths this weekend in St. Louis. As for Biles's selection, that bit of business is little more than a formality that will sort itself out very quickly.

Despite being one of the most decorated gymnasts of all time, Biles must earn her ticket to Tokyo where she is expected to be one of the Games headliners by adding to her haul of four gold medals from the 2016 Rio Olympics.

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The 24-year-old has won every all-around competition she has entered since 2013 and a loss in St. Louis would go down as one of the greatest upsets in U.S. sport.

Who will join Biles and Carey in Tokyo is not as clear cut.

The top two finishers in the women’s trials will earn spots on the four-member team. The other two members will be determined by a selection committee with one more individual quota spot to be filled.

Five alternates will be named for both men's and women's teams in case of a COVID-19 outbreak.

"If we have one team member who is exposed and then exposed the rest of the team and then potentially we have to replace the entire team that's why there are so many replacement athletes being named," USA Gymnastics president Li Li Leung said.

Talented field

Sunisa Lee and Jordan Chiles moved to the front of the pack with strong performances at the U.S. national championships earlier in June which served as a qualifier for the trials.

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Lee, second to Biles in the all-around at the nationals, and Chiles, who trains with Biles, would appear to have the inside track on two of the team spots. That leaves a talented field includes 2016 Olympic alternate MyKayla Skinner, Emma Malabuyo, Grace McCallum, and Leanne Wong scrambling for the fourth.

Competition will be no less fierce on the men's side where five spots (four team, one individual quota) are on the line.

Like the women, the top finisher will clinch a team spot while the runner-up also goes to Tokyo if he places among the top three on a minimum of three pieces of apparatus. Everything else will be decided by a selection committee.

The U.S. men are undergoing a changing of the guard led by 21-year-old Brody Malone who comes into the trials fresh off his all-around win at the national championships ahead of Yul Moldauer.

Sam Mikulak, a six-time national champion and the only member of the men's 2016 Rio Olympic team still competing, finished third at the nationals and is bidding for a spot on his third Games team.