Following a concussion suffered three months ago, NASCAR Cup Series champion Kurt Busch is retiring from full-time racing on the advice of his doctors.

The 44-year-old made the announcement Saturday at Las Vegas Motor Speedway, his home track and the place where he launched his career, the Associated Press first reported. In a press conference, Busch said doctors told him "it is best for me to 'shut it down,'" according to the report.

Tyler Reddick will replace Busch in the number 45 Toyota Camry at 23XI Racing for the 2023 season. Reddick had already planned to move to 23XI, the team co-owned by NBA legend Michael Jordan and NASCAR driver Denny Hamlin, from Richard Childress Racing (RCR) in 2024. He was able to switch teams a season early because RCR has signed Kyle Busch, Kurt's younger brother and a two-time Cup Series champion, for 2023.

Kurt Busch driving the number 41 Chevrolet SS in the NASCAR Cup Series

Kurt Busch driving the number 41 Chevrolet SS in the NASCAR Cup Series

Busch was injured in a crash in July and has missed 13 races so far. He's not the only Cup Series driver currently out with an injury; Alex Bowman has missed two races with a concussion and expects to miss three more, according to the AP. These injuries have led to questions about the design of NASCAR's Next Gen car, which was introduced this season.

Busch made his Cup Series debut in 2000 with Roush Racing in a Ford. Despite winning the 2004 championship with Roush, he was fired from the team and moved to Team Penske, which was then running Dodges, in 2006. His relationship with that team also ended poorly after the 2011 season, and Busch spent the next few years driving Chevys for a series of teams, including Stewart-Haas Racing.

His last two moves were to Chip Ganassi Racing, followed by 23XI for the 2022 season. A win in the number 45 Toyota at Kansas made Busch one of only a handful of drivers to race and win with every NASCAR manufacturer during his career.

Kurt Busch

Kurt Busch

Busch has won 34 races in 776 starts over 23 years, plus a 2017 Daytona 500 win. He also raced in the Indianapolis 500 and Rolex 24 at Daytona, and dabbled in drag racing.

Busch's departure marks the end of an era. He's the last active driver to have competed against the late Dale Earnhardt, and the last from the inaugural 10-car Chase for the Cup playoff in 2004, when he won his only title. Other stars from that era, such as Jeff Gordon and Jimmie Johnson, have already retired.

Busch reportedly plans to remain an ambassador for longtime sponsor Monster Energy, and has approached Fox Sports about commentary work.