Montgomery managed to stay in for two more plays before officially leaving Sunday's matchup. The other half of the Lions' destructive backfield with teammate Jahmyr Gibbs, nicknamed Sonic and Knuckles, will unfortunately be sidelined until next season, leaving third-string back Craig Reynolds to take up the mantle.
Montgomery had five carries for four yards along with four receptions for 31 yards in Sunday's 48-43 loss to Buffalo.
"Yeah, it looks like he's gonna require surgery that'll put him out for the rest of the year," said Lions head coach Campbell on Monday. "He had gotten it at some point yesterday in that game.
Montgomery has been stellar for the Lions this season, wracking up 775 rushing yards and 12 rushing touchdowns on 185 attempts. He was just two rushing touchdowns and 241 rushing yards from setting career highs.
Montgomery needed just 97 receiving yards and three receiving touchdowns to set career highs through the air as well.
The former 73rd overall pick in the 2019 draft signed a two-year, $18.25 million contract extension with the Lions this year, which will expire in 2028 making Montgomery an unrestricted free agent.