INDIANAPOLIS – A defense mired in a historic slump likely will be without its leader Sunday.

The Indianapolis Colts downgraded linebacker and defensive captain Zaire Franklin to doubtful for Sunday’s road test against the Carolina Panthers.

Franklin leads the NFL with 102 total tackles and 53 solos. He’s piled up at least 10 in seven of eight games. He set a franchise record with 166 tackles last season.

Franklin suffered a knee injury late in the second quarter of last Sunday’s loss to the New Orleans Saints. He was taken into the blue medical tent to be examined and then worked with the training staff on his movement.

He returned to the game and missed only two snaps and finished with a team-high 14 tackles.

However, the injury forced Franklin to miss all three practices this week.

If he misses the Panthers game as the downgrade indicates, that might mean an expanded role for Shaquille Leonard.

The Colts have been using Franklin, Leonard and E.J. Speed in their base defense, but kept Franklin and Speed on the field in their nickel package.

“I know I’m not in on third down,’’ Leonard said this week. “I kinda know exactly what it is. Like it or not, it is what it is.’’

That diminished role in Gus Bradley’s scheme – rehab from a second back surgery has contributed to that – has irritated Leonard.

“I feel like each week I prove who I am,’’ he said. “I feel like the way I play the game is getting better and better each week.

“But they say I don’t make enough splash plays, so I guess I’ll still be watching for a little bit.’’

Franklin’s injury could change that.

The defense can ill afford to maintain its poor play.

The Colts have allowed at least 37 points in three straight games – all losses – for the just the third time since 1984 and the first time since 2018.

Along with Franklin, they’ll also be without tackle Grover Stewart (suspended) and cornerback JuJu Brents (quad).

Roster move

The Colts elevated cornerback Chris Lammons to the active roster from the practice squad.

You can follow Mike Chappell on Twitter at @mchappell51.