Busch, the 2004 Cup champion, has been sidelined from competition since he suffered symptoms from a concussion in a 23 July accident during qualifying at Pocono.
The 44-year-old said on Saturday at Las Vegas Motor Speedway that he's “still not 100-percent and I’m still not cleared to race”, so could not commit to compete for a championship in 23XI's #45 Toyota next season.
“This is more of being unselfish and respecting what has to happen in this industry,” said Busch, who has won 34 races from 776 career Cup starts.
In a statement, 23XI Racing said it had reached an agreement with Richard Childress Racing to allow Tyler Reddick to join a year earlier than planned and step in for Busch next season.
“From the day Kurt Busch joined our team we knew he was going to elevate our organisation in many ways,” the 23XI Racing statement said.
“From earning 23XI our first playoff berth with his commanding win at Kansas Speedway to numerous hours spent off the track helping to grow our programme, Kurt has made us better.
“This season took an unexpected turn with his injury. Despite the unfortunate circumstances, Kurt has not stopped being a true professional and a trusted team-mate.
“We fully support Kurt’s decision to focus on his health and are grateful for his guidance as our team builds a strong foundation for the future.”
Busch has also shown interest in other forms of motorsports including sportscars (he was third in the 2008 Daytona 24 Hours) and the IndyCar Series (he finished sixth in the 2014 Indianapolis 500 in his lone series start).
“Kurt’s decision to step away from full-time NASCAR Cup Series competition next year is certainly not something anyone expected when we started the season together and celebrated in victory lane at Kansas Speedway earlier this year,” said Toyota Racing Development president David Wilson.
“Unfortunate circumstances led Kurt to a difficult decision, but we know that he will continue to contribute to the entire program at Toyota, TRD and 23XI Racing.
“He brings a tremendous amount of knowledge and firsthand championship experience to his team and fellow Toyota competitors.
“We’re here to support Kurt in this next chapter of his career and look forward to continuing to work alongside him.”
Busch’s tenure in NASCAR has included good and bad moments as vastly wide-ranging as perhaps any top-level driver in series history.
After skipping the second-tier Xfinity Series, he made his Cup debut with Roush Racing in 2001 and won 11 times over the next three seasons. He claimed the series championship in 2004, the first year of NASCAR’s playoff system, but was fired by Roush in November 2005 after being cited in an alcohol-related incident in Arizona and missed the final two races of the season.
Busch joined Team Penske for 2006 and won 10 races over the next six seasons, ranking fourth in the 2009 standings. He was released in 2011 and spent the next two seasons with fledgling teams Phoenix Racing and Furniture Row Motorsports before joining Stewart-Haas Racing for 2014, winning six times over five seasons.
In 2019, Busch and sponsor Monster Energy moved to Chip Ganassi Racing, where he won at least once each season during his tenure. The team’s sale to Justin Mark’s Trackhouse Racing put Busch’s future up in the air once again, but he was 23XI Racing’s first choice as driver when it planned an expansion to a two-car team this season.
Busch has not raced since his Pocono concussion, but said he was “at peace with where I am at”.
“This changes the course just a little bit,” he said. “Plenty of things to keep that passion alive and write that final chapter.”
