Los Angeles Rams head coach Sean McVay told reporters defensive tackle Aaron Donald suffered an ankle sprain during Sunday's loss to the Kansas City Chiefs.
Donald is undergoing testing to determine the severity of the setback.
The 31-year-old rarely misses any time because of injury, appearing in 127 of 129 possible regular-season games over his first eight years in the NFL. He made 65 straight regular-season starts from 2018-21.
Donald has also been a key contributor in the playoffs, tallying 3.5 sacks across four postseason games last year while helping the Rams win the Super Bowl.