MINNEAPOLIS (AP) — Each week, before Ryan Kalil gets going on Carolina's game plan and upcoming opponent, the eight-year veteran Panthers center has made a ritual of reviewing his younger brother's performances for Minnesota.

He has paid even closer attention this season. Matt Kalil has had his share of struggles at left tackle for the Vikings.

"I especially watch them when I know that he's hard on himself and he had a bad game and I just want to see what he's harping on," said Ryan, who has been in the NFL five years longer than Matt.

Ryan has analyzed Matt's blocking with a critical eye, but he also remains one of his biggest supporters. That's what family is for, after all.

"It's a lot easier on the inside where you're comfortable with a lot of guards. You get out on that island and it's a little bit tougher," Ryan said.

That rough season bottomed out last week when Matt was called for three penalties for 35 yards. On his way out of the stadium, he knocked a cap off the head of a heckler. The video went viral. Matt was on the phone with their father, Frank, when the exchange occurred.

"I asked my dad if he heard what happened. He said, 'Yeah, I heard the whole thing.' He said, 'It was a really ugly deal,'" Ryan said. "The guy called him over, said he was a big fan, asked for his autograph. ... Then he started saying some pretty ugly stuff to him. So I think my brother just kind of reacted. It's probably my fault for picking on him when he was little."

The Panthers visit the Vikings on Sunday. Hurting the team with holding calls and missed blocks, Ryan said, has been the hardest part for Matt this year. Matt has struggled with his confidence, partly due to "on and off" discomfort in the knee on which he had offseason surgery.

"You can't let that get the best of you. You've got to trust your abilities," Matt said.

Here are some key points to know about the game:

PLENTY TO PLAY FOR: Despite that ugly 3-7-1 record, the Panthers don't need any help to win the NFC South. They just have to win their final five games, including intra-division contests at co-leaders Atlanta and New Orleans, to repeat as NFC South champions. The Panthers, though, have they lost five straight games and are 0-3 coming out of their bye week under coach Ron Rivera.

"We're very lucky. Who knows what's going to happen?" Rivera said.

The Vikings at 4-7 would be tied for the NFC South lead, but they're out of the running in the NFC North. They gave Green Bay a good game last week in a 24-21 loss, after the division leader had won the previous two games by a combined 108-34 score.

"Nah, there's no moral victories in the NFL. It's a win or loss, and we didn't come out with a win," said cornerback Captain Munnerlyn, who spent the last five seasons with the Panthers.

TOLBERT'S BACK: Carolina's offense should get a boost with the return of Pro Bowl fullback Mike Tolbert, who missed the last eight games with a hairline fracture in his left leg. Tolbert is the rare hybrid who not only excels at blocking but can run well and catch passes. The Panthers haven't had a true fullback on the roster during his absence, so Tolbert ought to help open some holes for veterans DeAngelo Williams and Jonathan Stewart, who have struggled without him.

DEPLETED OFFENSE: The Vikings have had another unproductive season with the ball, ranking 28th in points and 30th in yards entering the weekend. Injuries have exacerbated their issues, and they just lost another starter in right tackle Phil Loadholt with a torn left pectoral muscle.

Five other regulars on the offense — quarterback Matt Cassel, running back Adrian Peterson, tight end Kyle Rudolph, right guard Brandon Fusco and wide receiver Jerome Simpson — have appeared in a total of 13 games. Rudolph is the only one who returned.

PROTECTING NEWTON: Panthers right tackle Nate Chandler suffered a season-ending right knee injury in a 19-17 loss to Atlanta before the bye week. Rivera picked Mike Remmers, who spent time on the practice squad with the Vikings earlier, to take Chandler's place. This has been a rough season up front, and only Kalil remains in place from last year's lineup. Four offensive linemen retired during the offseason, including stalwarts Jordan Gross and Travelle Wharton.

IMPROVING SECONDARY: Vikings defensive backs have 10 interceptions this year after totaling only six last season. The Vikings were 31st in the league in yards passing allowed in 2013; they're seventh in 2014.

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