Had their performances occurred in different seasons, there would be little doubt Minnesota Vikings running back Adrian Peterson and Denver Broncos quarterback Peyton Manning would both win the NFL Most Valuable Player Award for their efforts.

This year, though, those two will be competing against each other - as well as against other worthy candidates like Green Bay Packers quarterback Aaron Rodgers, Houston Texans defensive end J.J. Watt and New England Patriots quarterback Tom Brady - for the 2012 MVP Award.

While it's going to be a tough call for voters, the hardware ought to go to Peterson, who carried the Vikings to a 10-6 record and a berth in the NFC playoffs.

Manning, who battled back from four neck surgeries that completely erased his 2011 season, was amazing in his first season with the Broncos. He completed 400-of-583 passes for 4,659 yards, 37 touchdowns and 11 interceptions. His 105.8 quarterback rating was second only to Rodgers (108.0).

A four-time MVP, Manning guided the Broncos to a 13-3 record, including 11 victories in a row to close the regular season and nail down the No. 1 seed in the AFC playoffs. He took over as the quarterback of a team that went 8-8 and won a playoff game last season and elevated it to a much higher level. The Broncos have gone into this postseason as the odds-on favorite to win the Super Bowl.

Peterson tore both the anterior cruciate ligament and medial collateral ligament in his left knee on Dec. 24, 2011. Most observers expected Peterson to ease his way into this season, and perhaps not truly regain his burst and lateral ability until the 2013 campaign.

Defying all odds, Peterson was splendid right from the start of the season. He fell just nine yards shy of breaking Eric Dickerson's all-time, single-season rushing record, finishing with 2,097 yards and 12 touchdowns on 348 carries.

Rodgers led the league in quarterback rating, was second in the league with 39 touchdown passes and had a typically solid year for the Packers. Brady, meanwhile, was fourth in the league in both passing yards (4,827) and touchdown passes (34).

Despite those other performances, Manning would get the nod as the quarterback most deserving of MVP consideration. He had the second-most passing yards (4,659) and touchdown passes (37) of his illustrious career, and he had to build chemistry with an entire new organization and receiving crew in order to do so.

Watt, who was building momentum as an MVP candidate when the Texans looked like world-beaters during the first half of the season, finished with 81 tackles and 20.5 sacks.

What works against Watt, however, is that Houston's defense came back down to earth late in the season, and only three non-quarterbacks or running backs (defensive lineman Alan Page in 1971, kicker Mark Moseley in 1982 and linebacker Lawrence Taylor in 1986) have been voted NFL MVP.

With Manning and Peterson being the top two candidates, it seems easier to make a case for the Vikings' running back. While Manning is the person most responsible for making the Broncos an elite team, they were already pretty good before he got there.

With Tim Tebow calling the signals for much of the 2011 season, Denver went 8-8, won the AFC West title and topped the Pittsburgh Steelers in a wild-card playoff game. Manning improved the Broncos greatly, but they were a playoff- caliber team already.

Heading into the 2012 season, the Vikings were a fairly popular choice to "earn" the No. 1 pick in the 2013 NFL draft. Some of that gloom and doom prediction was the result of Peterson being expected to be less than 100 percent.

Peterson was better than ever, though. Incredibly, he collected 1,019 of his rushing yards after contact and ran for an average of 4.1 yards after the first hit by the defense. Peterson also lost just two fumbles on his 388 touches.

Minnesota's ability to win 10 games and be the NFC's biggest surprise playoff team was mostly the result of Peterson's performance. The rest of the Vikings' roster was rather ordinary, so Peterson had to gain all those yards against defenses designed to key on stopping him.

The Vikings ranked 16th in the league - right in the middle of the pack - in total defense. Second-year player Christian Ponder finished the season as only the league's 21st-ranked quarterback. Although dynamic wide receiver Percy Harvin (62 catches for 677 yards) was off to a flying start, he wound up missing the Vikings' last seven games.

Minus Harvin, Peterson was really the Vikings' only playmaker. Still, Minnesota went 5-2 in the seven games Harvin missed.

That happened because Peterson rushed for an average of 172.2 yards in five December games, leading the Vikings to four consecutive wins to close out the season. He broke the NFL record for rushing average per game for one month in a minimum of four games.

The Vikings finished only 20th in the NFL in total offense, but Peterson accounted for 43 percent of their yards from scrimmage. That's a hefty percentage for a running back, but, then again, not many running backs carry the ball 348 times and average six yards per attempt.

For comparison's sake, here's the percentage of their teams' total offense that the other top-five rushers in the league amassed: the Washington Redskins' Alfred Morris (27.6 percent), the Seattle Seahawks' Marshawn Lynch (31.8 percent), the Kansas City Chiefs' Jamaal Charles (34.2 percent) and the Tampa Bay Buccaneers' Doug Martin (33.1 percent).

Since 1987, 20 quarterbacks and seven running backs have been named NFL MVP. There were co-MVPs twice: Brett Favre and Barry Sanders in 1997, and Manning and Steve McNair in 2003. The last time a non-quarterback won the award was 2006, when it went to running back LaDainian Tomlinson of the San Diego Chargers.

Most of the time, a quarterback truly deserves to be the league MVP. After all, many teams have won championships with middle-of-the-pack running backs, but few have won with mediocre quarterbacks. Signal-callers are generally much more responsible for their teams' success (or failure) than any other players.

Occasionally, however, a running back can be the top MVP candidate. Those times only come around once or twice in a decade, but 2012 is one of those times. Peterson's season was one of the best ever compiled by a running back.

Jeff Saukaitis is a former Sports Network writer/editor who has been a professional sportswriter since 1985.