What do an embattled sophomore quarterback, defensive end and Mid-American Conference player have in common?

They all could be serious factors in one of the all-time great Heisman Trophy races.

To obtain a second Heisman, Texas A&M quarterback Johnny Manziel must stay eligible -- and perhaps eclipse the gaudy numbers he produced in 2012.

This year's candidates could emerge from unlikely positions such as South Carolina defensive end Jadeveon Clowney and unlikely places such as Northern Illinois quarterback Jordan Lynch. Michigan's Charles Woodson is the lone primarily defensive player to win the award. A MAC player has never clutched the trophy.

The list of other players to watch is lengthy and impressive. 

Oregon quarterback Marcus Mariota and burner De'Anthony Thomas could be popular picks among West Coast voters. Alabama quarterback A.J. McCarron and running back T.J. Yeldon are steady performers on the nation's preseason No. 1 team. Clemson's Tajh Boyd and Sammy Watkins are the nation's best pitch-and-catch combination. Quarterback Aaron Murray and running back Todd Gurley will gain momentum if Georgia enters the SEC title game undefeated.

Not every candidate must be paired with an equally talented player.

Quarterback Braxton Miller is primed to lead Ohio State to a second straight undefeated season, although a weak schedule could hurt him with some voters. Louisville quarterback Teddy Bridgewater also could lead his team to an undefeated season yet get dinged in the voting by a weak schedule.

USC's Marqise Lee might be the nation's top receiver. Northwestern's Venric Mark might be the nation's best multipurpose player. Baylor's Lache Seastrunk might rush for 2,000 yards.

It's possible somebody missing from the above list will enter the discussion.

Sign your name on a photo if you considered Manziel a Heisman contender last year at this time. Make sure you don't charge anybody for the signature.

-- Guy Cipriano | @newsheraldguy