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Duane Burleson, Associated Press
Detroit Lions tight end Tony Scheffler (85) hits the turf after catching a 17-yard touchdown reception in front of Carolina Panthers strong safety Charles Godfrey (30) and cornerback Captain Munnerlyn (41) in the third quarter of an NFL football game Sunday, Nov. 20, 2011, in Detroit. The Lions defeated the Panthers 49-35.

CHARLOTTE, N.C. — Ron Rivera arrived in Carolina with a reputation for transforming good defenses into great ones, which makes this season all the more frustrating for the first-year head coach.

There are some things even experts can't fix — like a surplus of injuries.

Five players have gone down with injuries, including three starters. Several other players have missed games forcing the Panthers to start nine different defensive lineups in 10 games.

And now the problem may be getting worse.

Rivera said defensive end Charles Johnson, the $76.5 million pass rusher who leads the team with seven sacks, was scheduled to have an MRI after taking a shot to back of the shoulder Sunday and linebacker Omar Gaither re-injured his knee.

James Anderson, one of only two linebackers from the original eight who has yet to miss a game, walked through the locker room Monday with his right foot in boot. Linebackers Dan Connor and Jason Phillips are still recovering from injuries that kept them out on Sunday. And defensive end Greg Hardy is nursing a twisted ankle, although Rivera doesn't believe it's serious.

What is serious is Carolina's inability to stop anyone of late — at least on a consistent basis.

The Panthers have surrendered 79 points over the last two weeks, including 35 in the second half of Sunday's 49-35 loss to the Detroit Lions. Matthew Stafford threw for a career-high five touchdowns and running back Kevin Smith, out of the league just two weeks, had 201 yards from scrimmage and scored three times.

Rivera called Sunday's outing "as rough as any I've been around" in 15 seasons as a professional coach. The Panthers allowed a franchise-record 495 yards. Although the Panthers defense started strong by forcing turnovers on Detroit's first three drives, they fell apart after that allowing the Lions to score seven touchdowns on their final nine drives.

The Panthers (2-8) now rank 27th in the league in yards allowed per game, a far cry from the unit Rivera coached last year in San Diego that finished first in defense.

Only this week's opponent, the Indianapolis Colts, have given up more points than the Panthers.

With players shuffling in and out of the lineup, the training camp plans Rivera and defensive coordinator Sean McDermott had to be an "aggressive, attacking-style defense" have long ago been abandoned. Right now the Panthers are just hoping to get everyone on the same page.

What seems to frustrate Rivera the most is the team's inability to get off the field on third down. He pointed to a crucial third-and-12 during the second quarter with the Panthers leading by 17 points. The Panthers botched the coverage and Stafford completed a 15-yard pass to Nate Burleson for a first down that would lead to a Lions touchdown.

"We get them off on third down, they punt, we get good field position, we go down and score and now it could have been 31-7," Rivera said. "We have to have a killer instinct."

Defensive end Thomas Keiser, who was one of the few players to get pressure on Stafford, acknowledges that seems to be lacking with this team.

"Unfortunately I would have to say the killer instinct is lacking right now," said Keiser, who recorded both of Carolina's sacks. "Just to be able to be relentless when you have a foot on a team's throat and grind your heel even harder. We didn't do that (Sunday)."

That's been the case most of the year.

The Panthers have had a chance to win every game except one in the fourth quarter. Even Sunday the Panthers battled back to tie the game at 35 midway through the fourth quarter on a two-point conversion pass from Cam Newton to Steve Smith, only to watch the Lions go 80 yards in 2:27 for the go-ahead touchdown.

"The situation that has to happen is we've got to find a way to not to worry about losing again and worry about winning again," Rivera said. "I think that's part of our problem — when something bad happens the wind goes right out of our sails."

Injuries forced the Panthers to start Jordan Senn at middle linebacker. Senn started the season fourth on the depth chart at that spot and was kept around primarily for his special teams ability.

McDermott, who came to Carolina after being let go by Andy Reid in Philadelphia, said he still has faith in the guys in the defensive meeting room. He said the struggles aren't from a lack of effort. A lack of experience and knowledge of the defense perhaps, but not a lack of effort.

But like Rivera he refuses to blame the problems on the mounting injuries.

"It's the hand you're dealt," McDermott said. "That's what we deal with in this league. I trust those guys in that room to make plays and they haven't given up. We're building something here — something more than what most people see. And we have to continue to build. That core of what we're building will carry us through this time and we'll use it next year to look back on and say, 'hey, remember where we were.'"