"This was absolutely a missed opportunity for the NCAA," he said. "The NCAA has been using a policy for over 10 years now, and it's been working quite well."
He added, "It really seems like they made a knee-jerk reaction decision to what's currently happening in the NCAA right now with the participation of a single athlete."
The NCAA updated its policy on the participation of transgender athletes this week, leaving it up to the national governing body for each sport to determine eligibility requirements.
The policy change aligns with recent changes made by U.S. Olympic Committee and International Olympic Committee, the organization said in a statement. If the national governing body of a sport does not have a policy, the NCAA would apply the rules of that sport's international federation or the IOC's policy.
"We are steadfast in our support of transgender student-athletes and the fostering of fairness across college sports," John DeGioia, chair of the NCAA's Board of Governors and Georgetown University president, said in a statement. "It is important that NCAA member schools, conferences and college athletes compete in an inclusive, fair, safe and respectful environment and can move forward with a clear understanding of the new policy."
The new policy goes into effect immediately and will start with the 2022 winter championships.
Mosier, however, said that he sees challenges with the rule's implementation.
"It's going to be difficult for both the NCAA to manage compliance with these rules, as well as for athletes and coaches to figure out what they need to do to be in compliance with these rules," he said. "I'm really worried about the transgender and nonbinary young people who are seeing this policy, who are wondering if it's possible for them to be their authentic selves and continue to play the sports that they love."
The debate around transgender athletes' participation in college sports has been brought to the forefront after trans University of Pennsylvania swimmer Lia Thomas broke several records in women's swimming.
Thomas realized that she was transgender in 2018, she said in an interview on the "SwimSwam" podcast in December. Unsure if she would be able to continue swimming, she delayed coming out and competed on the University of Pennsylvania men's team for the 2018 to 2019 season.
The experience "caused a lot of distress in me," Thomas said on the podcast.
"I was struggling, my mental health was not very good," she added. "It was a lot of unease, basically just feeling trapped in my body. It didn't align."
Thomas started to transition in 2019. She completed a year of hormone therapy, which is what the NCAA requires for trans women to compete on women's teams. After the 2020 to 2021 season was canceled due to the COVID-19 pandemic, she joined Penn's women's team for the 2021 to 2022 season.
After the NCAA announced its rule change, Penn Athletics released a statement Thursday saying that it would support Thomas.
"Penn Athletics is aware of the NCAA's new transgender participation policy," it said. "In support of our student-athlete, Lia Thomas, we will work with the NCAA regarding her participation under the newly adopted standards for the 2022 NCAA Swimming and Diving Championship."
In a statement, the College Swimming & Diving Coaches Association of America said it supported Thomas but denounced the policy change.
"Yesterday's Board of Governor's decision is not a solution," it said, according to the statement posted on Instagram Thursday. "The NCAA's previous policy on transgender participation, while pioneering, was outdated and yesterday's decision is a missed opportunity to lead this important discussion."
The organization called for the NCAA to add an additional qualifying spot for this year's championships.
Before the NCAA announced the policy change, several prominent athletes criticized Thomas' participation in women's sports, including former Olympian Caitlyn Jenner, who came out as trans in 2015.
"Number one, biological boys -- I've said from the beginning -- should not be playing in women's sports," she said in an interview with Fox News. "We need to protect women's sports."
While Jenner said she respected Thomas' decision to "live her life authentically," she added later that "her respiratory system is bigger. Her hands are bigger. She can swim faster. That's a known. All of this woke world that we're living in right now is not working."
Five-time Olympic swimmer Michael Phelps also discussed Thomas in a recent interview with CNN.
"We all should feel comfortable with who we are in our own skin, but I think sports should be played on an even playing field," he said in the interview. "I don't know what that looks like in the future but it's hard."
According to Axios, Thomas has qualified for the NCAA's swimming championships in March.
ABC News' Kaylee Hartung and Sean Sanders contributed to this report.