Colin Kaepernick, QB, San Francisco 49ers: Through a season and a half, the 49ers with head coach Jim Harbaugh and quarterback Alex Smith were one type of team -- a team with a powerful, multiple run game, a great defense, and the kind of passing game that was generally better at maintaining a lead than fighting back from an extreme deficit. Smith was a good enough quarterback, but the 49ers knew that they couldn't expect a heavy diet of explosive plays. That changed when Kaepernick, the second-year prop from Nevada, usurped Smith after the veteran suffered a concussion against the St. Louis Rams in early November. Kaepernick proved that he had the arm, mobility, and game acumen to give his team a new element for opposing defenses to worry about. [ Related: Colin Kaepernick further validates Jim Harbaugh's decision to start him ] Never was that more apparent than in San Francisco's 41-34 Sunday Night Football win over the New England Patriots. Kaepernick threw four touchdown passes to three different receivers, and added 28 yards rushing to befuddle a Patriots defense that knew what it was dealing with in Kaepernick ... and was unable to stop it. Kaepernick will have obvious moments of inexperience in what is essentially his rookie campaign from an experience perspective, but when he's on, he makes the 49ers nearly impossible to beat. J.J. Watt, DL, Houston Texans: Speaking of "impossible to beat," there's Watt's three-sack performance against the Colts in a 29-17 win that gave the 2012 AFC South crown to the Texans, and Watt a tie with San Francisco's Aldon Smith for the NFL's sack lead at 19.5. Watt had 10 total tackles, proving once again that he is an underrated run-stopper, but his true value is in his ability to get after the quarterback -- and right now, nobody does it better. Relying on an ever-increasing array of hand moves and advanced techniques to beat the daylights out of the poor offensive linemen who have to deal with him, Watt has become the type of player we've rarely seen. He can rush with the speed of an elite defensive end from the edge, and also bull through guards and centers with the best defensive tackles. Adrian Peterson may have taken the NFL MVP vote -- at least for now -- but Watt could very well be the league's most valuable defender, and he is probably that in a relative landslide. Russell Wilson, QB, Seattle Seahawks: "I'm just thrilled that he's been able to continue to grow," Seahawks head coach Pete Carroll said of his rookie quarterback after he racked up three rushing touchdowns and helped Seattle become the first team since the 1950 Los Angeles Rams and the 1950 New York Giants to score 50 or more points in two straight games. "For a time, we were just trying to get the offense going and not screw it up and make sure he could keep growing. Well, we're past that now." Indeed they are. Not only has Wilson shown a comprehensive command of Seattle's passing offense at its highest level, but his mastery of the zone-read rushing concepts installed by offensive coordinator Darrell Bevell has made Seattle's offense really tough to deal with -- not only when they're facing relative creampuffs like the Arizona Cardinals, but also when they catch fire against better defenses like the Chicago Bears. In Seattle's 50-17 thrashing of the Bills on Sunday, Wilson also threw his 21st touchdown pass of the season, keeping him ahead of all rookie quarterbacks -- yes, even Andrew Luck and Robert Griffin III -- and tying him with Cam Newton for the second-most TD passes by any rookie in NFL history. Peyton Manning had 26 in his rookie campaign, and we wouldn't be surprised if Wilson matches that, as well. Adrian Peterson, RB, Minnesota Vikings: