Another Olympic gold medal hopeful will not compete in the Tokyo Olympics.

Katie Lou Samuelson, a key member of Team USA's first-ever 3x3 women's basketball team, was placed in COVID-19 health and safety protocols on Saturday and will not compete in the tournament, USA Basketball announced on Monday.

"Our hearts are broken for Lou," USA Basketball 3x3 said in a statement on Twitter. "We thank her for her endless commitment to building up USA Basketball 3x3 & we will miss her dearly in Tokyo."

Samuelson, a member of the Seattle Storm, will be replaced by Las Vegas Aces guard Jackie Young. She joins Kelsey Plum (Aces), Allisha Gray (Dallas Wings) and Stefanie Dolson (Chicago Sky) for the U.S.

Samuelson will miss 3x3 debut

Samuelson, 24, won 3x3 gold medals at the 2014 Youth Olympic Games and the 2013 FIBA U18 Wold Cup. She would have been the first USA Basketball player to compete at both the Youth Olympic Games and Olympics.

She said on Instagram she fell ill with COVID and is devastated to miss the Olympics. She said she is part of the 99 percent of WNBA players who are fully vaccinated.

The former UConn Huskies star has experienced a string of tough breaks in her young career. She broke her foot as a freshman during the 2016 national semifinals and couldn't play in the final that UConn won. She had to undergo ankle surgery following her junior year. In 2019, her rookie year with the Chicago Sky, she missed time with a hand injury.

Samuelson is coming off a breakout season in Europe that closed with a Spanish League title while playing for Perfumerías Avenida. She was named to the All-EuroLeague first-team and is a leading contributor for the Storm behind Olympians Breanna Stewart, Jewell Loyd and Sue Bird.

Young joins 3x3 in Olympic debut

Samuelson, Plum, Gray and Dolson clinched the United States spot in the tournament in May at the Olympic qualifying tournament. They were chosen by USA Basketball to continue representing the nation on the Olympic stage.

The 3x3 competition is part of the Olympics for the first time this year. It's a half-court game played to a maximum 10 minutes with a 12-second shot clock. Baskets inside the arc are worth one point and outside the arc are worth two. Free throws are also one apiece. The first team to 21 wins, or whichever team is leading at the 10-minute mark.

Young, a third-year player who entered the draft as a junior out of Notre Dame, played on the USA Basketball 3x3 team during the 2019 World Beach Games. The team went 3-1, losing in the quarterfinals to Brazil. She was also part of the team's training camp in February 2020.

The U.S. is set to play France followed by Mongolia to open the tournament on Saturday. There are eight teams in total competing.

Positive tests piling up ahead of Olympics

Positive tests are beginning to pile up in Japan where athletes and media members are still arriving and currently training for the Games that officially begin Friday at the Opening Ceremony. Other competitions begin earlier in the week.

Tennis star Coco Gauff had to pull out of the Olympics on Sunday with a positive COVID-19 test. An alternate for the U.S. women's gymnastics team also tested positive in recent days, the organization announced Monday. And Bradley Beal has been ruled out for the men's basketball team for the same reason.

Positive tests have also impacted other countries as they descend upon Japan, a country that is largely unvaccinated and has seen an increase in case numbers over the past few weeks.

More Olympics coverage from Yahoo Sports:

• Wetzel: Olympics already at risk as U.S. gymnast contracts COVID

• Coco Gauff out of Games due to positive COVID test

• Liz Cambage under investigation for alleged altercation

• U.S. men's basketball beats Spain in final exhibition game