While two quarterbacks have hogged a lot of the Rookie of the Year attention this fall, there are several lesser-known prospects turning heads four weeks into the 2012 NFL campaign.

No doubt, Andrew Luck and RG III have dominated early talk about NFL rookie of the year candidates. But they're not the only two making their mark.

From wide receiver to running back, linebacker to safety, the league has a bevy of impact players this season—most expected, some unexpected.

Either way, watching rookies explode onto the scene is part of what makes the NFL so much fun to watch every year.

Here is our list, with one fourth of the season just about wrapped up, of the to Rookie of the Year candidates at every position.

Running Back: Trent Richardson, Cleveland Browns

Trent Richardson, the third overall pick in this year's draft, leads AFC rookies in rushing and is the favorite Rookie of the Year candidate at running back four weeks into the season.

Through four weeks, Richardson rushed for 222 yards on 64 carries and three touchdowns. He has 4.4 speed, can pound the middle and has good hands out of the backfield.

The Browns offensive line is solid, though if rookie quarterback Brandon Weeden does not progress as the year goes on, teams will load the box to stop Richardson.

Despite a decent crop of rookie running backs Richardson is the cream of the crop and has the best opportunity to get enough snaps to shine.

Quarterback: Robert Griffin III, Washington Redskins

The big debate coming into the 2012 NFL season was who would be better, Andrew Luck or Robert Griffin III?

I was in RGIII's camp early, and I'm still going with the Baylor standout as the top Rookie of the Year prospect at quarterback.

And why not? Griffin has completed 67 percent of his passes for 747 yards and has thrown four touchdowns to just one interception.

He has also proven just as deadly when running the ball, garnering three touchdowns on the ground and over 200 yards rushing.

He is clearly the class of the 2012 draft.

Cornerback: Morris Claiborne, Dallas Cowboys

The Dallas Cowboys rookie cornerback Morris Claiborne came into the season with high expectations and so far is fulfilling them quite admirably.

Claiborne, the LSU standout, has some work to do to mirror his NCAA success, where he logged 51 tackles, six passes broken up and six interceptions for a Tigers team that made it to the BCS Championship game last season.

In three games, Claiborne has just six tackles and no picks. But he helped the Cowboys shut down Eli Manning in the season opener—Manning had just 213 yards and averaged just 6.7 yards per pass—even though he was the target the Giants attacked with Brandon Carr on the other side of the field.

Claiborne has the skills to become the Cowboys' first true shutdown corner since Deion Sanders, dominating games with his ability to tackle in the open field, break up the big play and use his athleticism to come down with the interception in traffic.

Linebacker: Luke Kuechly, Carolina Panthers

The 2012 draft was solid at linebacker, with a handful of college stars poised to make a big impact on the NFL stage.

But Luke Kuechly of Boston College stood out among the rest.

He was the first linebacker drafted, at No. 9, and four games into his rookie campaign for the Carolina Panthers, he is not disappointing.

Kuechly, through four games, has 21 tackles, including nine solo tackles, and was a force to reckoned with Sunday in the Panthers' last-minute loss to the Atlanta Falcons, racking up five tackles, three of them solo.

He drives to the ball as well as anyone in the game, is in on gang tackles and performs well in the open field as well.

Defensive Line: Bruce Irvin, Seattle Seahawks

Dontari Poe, Fletcher Cox and LSU's Michael Brockers went Nos. 11, 12 and 14 in the NFL draft.

Bruce Irvin was not expected to go in the first round.

Instead, the Seattle Seahawks chose him with the No. 15 pick as many scouts and talking heads rolled their eyes.

Irvin was oh-fer in his first two games, not recording a single tackle, sack or pick.

But in last Monday night's game against the Green Bay Packers, he sacked Aaron Rodgers twice and got credit for another half a sack before the infamous catch/touchdown that won Seattle the game.

Irvin was as big a dark horse as there was in the NFL draft, and on paper he still has a lot to prove, but he will prove worth the pick.

Offensive Line: Matt Kalil, Minnesota Vikings

Matt Kalil, the USC standout, was brought to Minnesota to help anchor the left side of the Vikings offensive line and protect the developing Christian Ponder.

Kalil, the 6'7", 308-pounder, has done just that.

The Vikings, 3-1 after four weeks, have won with defense and a confident Ponder spreading the ball around, with Kalil anchoring the left side.

Ponder is off to his best start yet, has escaped pressure and minimized sacks through four games and has yet to throw a pick. The Vikings O-line has improved overall, but Kalil is a big, big part of that.

He's clearly the class of the draft on the offensive line.

Wide Receiver: Kendall Wright, Tennessee Titans

Baylor's Kendall Wright teamed with RGIII to forge one of the NCAA's most dangerous tandems last season.

Wright caught 108 passes for 1,663 yards and 14 touchdowns in 2011, and this year he has made the adjustment to the NFL better than any other wide receiver standout.

In four games with the Tennessee Titans, Wright has brought down 14 passes for 102 yards and one touchdown, besting both Justin Blackmon and Michael Floyd, who were drafted higher than him.

Wright has blazing speed and strong hands, making him tough to catch and tough to defend.

In the end, Blackmon and Floyd may prove the better long-term investment, but Wright is showing he could be a solid Rookie of the Year candidate.

Safety: Mark Barron, Tampa Bay Buccaneers

The Tampa Bay Buccaneers' Mark Barron was the top safety coming out of college this year, and he has proved the prognosticators right.

Through three games, Barron had 19 tackles—an amazing 15 were solo tackles—and he has racked up some heavy hits in the season's opening weeks, including one on opening day that knocked veteran receiver Steve Smith silly.

The Alabama alum has helped invigorate a Bucs defense that was dead last in the league last year, along with help from Tampa Bay's old school holdout, Rhonde Barber.

Last year, Barron garnered 68 tackles (43 solo), two picks, one sack and countless broken up passes and tackles for a loss for the national champion Crimson Tide.

This year he's making opposing offenses see red whenever they come his way.

Kicker: Blair Walsh, Minnesota Vikings

The Minnesota Vikings' rookie kicker nailed all four field-goal attempts in the Vikes' season-opening victory over the Jacksonville Jaguars, and he hasn't let up since.

He missed his first field goal as a pro in the Vikes' 20-13 win over the Detroit Lions on Sunday, but nailed another from 50 yards out earlier in the game.

He is now 9-for-10 and has kicked at least one field goal of 50 or more yards in each of the Vikings' four games.

Walsh is looking about as automatic as the Giants' Lawrence Tynes at this point of the season and is no doubt the best rookie kicker in the game thus far.