OWINGS MILLS, Md. -- The belief is that Baltimore Ravens linebacker Teddye Buchanan tore his ACL in Sunday's 24-0 win at the Cincinnati Bengals, a source told ESPN's Adam Schefter, which would mean the team's second-leading tackler would be out for the remainder of the season.
Buchanan will undergo additional testing to confirm the injury, the source added.
A rookie fourth-round pick, Buchanan injured his right knee on punt coverage in the first quarter and was carted off to the locker room. He left the stadium using a cane.
Buchanan is the second defensive starter that Baltimore would lose for the season. Pro Bowl defensive tackle Nnamdi Madubuike suffered a season-ending neck injury in Week 2.
This would abruptly end Buchanan's highly productive first season. He had been one of the biggest surprises on the Ravens this season, making 11 starts after replacing Trenton Simpson at weakside linebacker.
Buchanan, 23, entered Sunday's game with 83 tackles, which trailed only middle linebacker Roquan Smith (100 tackles). He also added five tackles for a loss, two quarterback hits and a half sack this season.
"It sucks anytime you see your guy go down, somebody you go to war with every day and truly just a good dude," Smith said after the game. "It's giving me chills thinking about it, and just knowing what [Teddye Buchanan] stands for, knowing all that he's gone through. Obviously, it's an unforgiving business, and we know that. We signed up for that, and it just sucks, but I know it's a minor setback for him."