Carolina Panthers wide receiver Kelvin Benjamin (13) is tackled by Cincinnati Bengals cornerback Adam Jones (24) in the first half of an NFL football game, Sunday, Oct. 12, 2014, in Cincinnati. (AP Photo/Paul Sancya)

CINCINNATI (AP) -- Rey Maualuga and Emmanuel Lamur missed practice again on Thursday, leaving the Bengals' struggling defense without two of its mainstays heading into one of its biggest challenges.

Cincinnati (3-1-1) is coming off a bad two-game stretch on defense. The Bengals have given up 936 yards and 77 points during a loss at New England and a tie with Carolina. They've also gotten their linebacker group depleted - Maualuga has a severe hamstring injury, and Lamur has an injured shoulder.

The Bengals have finished in the top 10 in defense during four of the last five seasons, so nobody saw this downturn coming.

''Defensive players - they're different,'' coach Marvin Lewis said. ''You shake them up, and be careful what you get out of it when you open the cap. We see it daily. You have to make sure they're all pulling in the same direction or else they'll tie some knots quickly.''

It's very uncharacteristic for a unit that finished third in the NFL last season and returned virtually all of its starters. The defense played well during a 3-0 start, but has dropped to 28th overall in the league after the two poor showings.

''Like I told the players, you played pretty good in the first three games and you start to think you're pretty ... good,'' defensive coordinator Paul Guenther said. ''So we've got to come back with good focus this week and get back to playing like we can.''

They play on Sunday at Indianapolis (4-2), which has the league's top-ranked offense. Lewis acknowledges it will be a big moment for a defense that's gotten its pride hurt.

Lewis was watching video of how the defense played after the 37-37 tie against Carolina on Sunday night when linebacker Vontaze Burfict called to vent.

''He was looking at the tape as well at the same time and we were both as equally disgusted at our play,'' Lewis said. ''We took turns not doing our jobs. I could put two plays together for every player where they played brilliantly, and I could put a play where they didn't do what they're supposed to do exactly.''

It's not just one area of the defense.

The line has been the strength of the unit, getting pressure on the quarterback without having to blitz. Teams have kept in extra blockers, and the line hasn't consistently gotten pressure. The Bengals have eight sacks - only seven teams have fewer - including only one in the last two games.

The Patriots piled up 505 yards - the most against a Cincinnati defense in seven years - and Carolina turned Cam Newton loose for 107 yards rushing. The back-to-back showings have tarnished the defense's reputation.

''Let's just not let the moment slip away,'' cornerback Adam ''Pacman'' Jones said. ''I think everyone in here knows what we're trying to do and I think we'll be all right.''

For the first time this season, the defense self-destructed with penalties against the Panthers, extending four scoring drives. Cincinnati was penalized 13 times for 119 yards overall. The defense was flagged seven times. Burfict got two personal fouls and an illegal contact penalty.

Until Sunday, the Bengals were among the league's best at avoiding penalties. Their previous high for a game was seven penalties.

The last time the Bengals were penalized 13 times was on Sept. 20, 2009 against Green Bay, according to STATS.

''It's probably the most penalties I've seen on our defensive side of the ball in years,'' defensive tackle Domata Peko said. ''That's something that's on us that we have to clean up as a unit and as men.

''We've got to look in the mirror and see how we can fix this.''

Notes: Receiver A.J. Green didn't practice on Thursday, resting his injured right big toe. He was inactive against the Panthers and isn't expected to play in Indianapolis. ... Guard Kevin Zeitler had a second full practice, an indication he'll return on Sunday. He's been sidelined since the second game of the season with an injured right calf. ... The Bengals made two practice squad moves. They re-signed rookie LB Khairi Fortt, who had been waived two days earlier. Also, they released second-year guard Jeff Baca, who joined the practice squad a week earlier.

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