NFL Whip Around: What we're watching in Week 15

SAN DIEGO – There has been plenty of social media and sports radio hand-wringing in the Rocky Mountains after Denver Broncos quarterback Peyton Manning posted back-to-back games with less than 200 passing yards and saw his 51-game streak of games with a touchdown pass broken last week.

Count Manning's former offensive coordinator – and this week's opposing head coach – as those who don't believe there is anything wrong with Manning's passing game.

"I don't know what film everyone is looking at to say that. He's been one of the best in the business, he's been for a long time," San Diego Chargers head coach Mike McCoy said Friday. "I got no idea where that's coming from."

McCoy instead is relying on his inside information about Manning from the season they spent together in Denver in 2012, and recent memories of Manning's three-touchdown, no-interception performance against McCoy's Chargers on Oct. 23.

Still, there is no doubt the Broncos' offense has evolved since that Thursday night game in Denver, thanks to a commitment to the run game over the past three weeks, with the physical, power running style of C.J. Anderson and Juwan Thompson. Thompson, an undrafted rookie from Duke, scored two touchdowns against the Chargers, but Anderson, now Denver's starter, had just one carry for no yards in that October game.

Chargers wide receiver Keenan Allen was Anderson's teammate at the University of California, and has some advice for his defensive teammates about defending Anderson: gang tackle.

"You have to wrap him up. Swarm to him," Allen said. "He'll definitely break a tackle."

Now on to the NFL Whip Around, a guide to Sunday's hottest stories.

Johnny Manziel's debut

Need to know: Thanks to Johnny Manziel's debut as the Cleveland Browns' starting quarterback, Sunday's game between the Browns' and the Cincinnati Bengals is now a must-watch even for those without a rooting interest in the AFC North. Such is the power of Manziel – as unique a player and as polarizing an athlete as the NFL has seen in years. The Browns, after losses to Buffalo and Indianapolis in the past two weeks, have reached the point of desperation, and need Manziel to provide some sort offensive spark to get back into the race for the division title.

What to expect: This is a guarantee – no matter what Manziel does on Sunday, it won't be boring. He will inject energy into the Browns' offense and into the crowd at FirstEnergy Stadium, and it will be interesting to see how that carries over into the actual game plan. Look for offensive coordinator Kyle Shanahan will be able to dig into a different section of his playbook, call on Manziel's legs for bootlegs, read-option plays and quarterback scrambles to give the Browns a different look than they had with Brian Hoyer.

Last gasp for San Francisco?

Need to know: The Arizona Cardinals, with their 12-6 win against St. Louis on Thursday night, put pressure on the Seattle Seahawks to win Sunday against San Francisco, lest they fall two games back in the NFC West. Those are important stakes for the Seahawks, who currently own the head-to-head tie-breaker against Arizona. But San Francisco might have even more to play for. After consecutive losses to Seattle and Oakland in the past two weeks, the Niners are out of the division race and need a win to remain in the wild-card hunt.

What to expect: The 49ers have not won a game in Seattle since early 2012, and are heading to CenturyLink Field at a bad time, with the Seahawks finally starting to resemble the team that won the Super Bowl last year. San Francisco quarterback Colin Kaepernick's struggles always seem worst against the Seahawks, like when he threw two interceptions in a Thanksgiving night loss to Seattle. Unless the 49es have magically rediscovered their running game, and Kaepernick regained his confidence in the past week, this game could wind up as another Seattle blow out.

Cowboys' chance for redemption

Need to know: After an embarrassing 33-10 Thanksgiving Day loss to the Philadelphia Eagles, the Dallas Cowboys on Sunday get their chance for some NFC East revenge in a game that will play a significant role in determining the NFC East champion. The Cowboys hardly looked like a team that deserved to make the postseason when they got run over by LeSean McCoy in that Week 13 game, but now we'll get to see what a 10-day break – and crucial rest for Dallas quarterback Tony Romo – for a Cowboys team that is so desperate to make the playoffs for the first time since 2009.

What to expect: Though the Cowboys will need Romo to avoid another multiple-interception day like he had on Thanksgiving, once again the most important player for the Dallas offense this week should be running back DeMarco Murray. Murray, the NFL's rushing leader, had a season-low 73 yards (on 20 carries) in the first game against Philadelphia, in the only game in which he's averaged less than four yards per carry all season.

GAME TIME DECISION: San Diego Chargers running back Ryan Mathews had to miss his team's first game against the Broncos in October because of a knee injury, and now he's in danger of missing Sunday's game because of an ankle injury he suffered last week against the New England Patriots. Mathews did not practice all week, but McCoy declined to rule him out yet, and instead has listed Mathews as questionable, believing that Mathews knows the game plan and Chargers' offense well enough that he could play without practicing, should his ankle improve by Sunday morning. Should Mathews be inactive, the Chargers will rely on rookie Branden Oliver, who had 13 rushes for 36 yards against the Broncos in October, and Donald Brown, who missed the first Denver game because of a concussion.

FANTASY PLAY: With Carolina Panthers' starting quarterback Cam Newton out this week while recovering from the back injury he suffered in a car accident, the Panthers' running game could be even more important Sunday against Tampa Bay. That could mean another big day for running back Jonathan Stewart, who had 20 carries for 155 yards last week against the New Orleans Saints. Stewart has now averaged more than seven yards per carry in his past two games.

FOR ENTERTAINMENT PURPOSES ONLY: Las Vegas still has faith in the Kansas City Chiefs. Despite losing three consecutive games, the Chiefs are listed as a 10-point home favorite against the Oakland Raiders. Yes, the same Raiders who beat San Francisco last week and upset the Chiefs in Oakland three weeks ago. But the Chiefs are desperate to hang in the AFC wild card race and could be due a big game from running back Jamaal Charles.