A perfect example would be Emmitt Smith, who just got inducted into the Pro Football Hall of Fame this past weekend. Quite a few experts, including Mel Kiper JR. himself, didn't think Smith had the size to be a successful running back in this league. What did he end up doing? Oh, nothing big. Just finishing his career as the league's all-time leading rusher.
Other more recent guys, i.e. Steve Slaton and Matt Forte had great rookie campaigns but have fallen since then.
This year's rookie class seems to be pretty deep when it comes to running backs. Here's the guys you may want to keep an eye on this pre- and regular season.
Top Five (rankings, stats according to ESPN.com's fantasy game):
1. Ryan Mathews, San Diego Chargers
Taken with the 12th overall pick in the draft, Mathews' stock is rising with the absence of Canton-bound Ladainian Tomlinson, who left for New York this offseason. San Diego's other running back Darren Sproles seems to have the most success as a third down back/return man, meaning Mathews should get quite a few carries. He is the only rookie running back who is projected for 1,000 yards this season.
2. Jahvid Best, Detroit Lions
Despite playing his ball in Detroit this season, I think Best has the most upside out of all of this year's running back class. The fastest back drafted, Best is the biggest threat coming out of the backfield as well and is owned in 100% of ESPN's fantasy leagues. Don't be surprised if Jahvid (projected for 660 rushing yards, 364 receiving yards and six TDs) has a solid preseason and starts ahead of Kevin Smith week one, especially because of Smith's injury.
3. C.J. Spiller, Buffalo Bills
With Marshawn Lynch's days in Buffalo numbered, Spiller could see more touches come his way as the season progresses. Despite being the first running back selected (No. 9 overall), Spiller is only projected for 800 yards and four touchdowns.
4. Montario Hardesty, Cleveland Browns
Last year's eighth-best rushing offense gets a huge boost from Hardesty after being taken in the second round. Projected in the top 50 backs, Hardesty is projected for 800 yards and eight TDs in 2010. Hardesty wont be the opening weekend starter, but will see quite a few carries come his way considering Jerome Harrison has yet to carry the load full-time and may need some help carrying the team.
With Steve Slaton disappointing, Houston needed to get another top-tier running back in the draft, which is why they selected Tate in the second round. Tate, projected for 600 yards and eight TDs, has a lot of potential and could easily land the starting role in the preseason. Tate's combination of size and speed gives Houston the perfect feature back for years to come.
Also published on Bleacherreport.com