This is the second article in a series previewing the top NFL prospects by position for the 2010 draft.

This year's RB class features two dynamic runners — Clemson senior C.J. Spiller and California junior Jahvid Best — and a solid but unspectacular group of big backs, led by Georgia Tech junior Jonathan Dwyer. Spiller is a game changer with good hands — if he can stay healthy in the pros, he could become a Pro Bowl-type talent. The inability of Reggie Bush to change games in the pros the same way he did in college, however, has forced teams to view multipurpose backs in a different vein, and it's possible no back is drafted in the top 10 again this year.

Note: "e" indicates the height, weight or 40-time is estimated.

SENIORS

1. C.J. Spiller, Clemson
5-11e, 195e, 4.3e

An electric talent with rare acceleration, Spiller is a game-breaking runner and returner capable of flipping the field every time he touches the ball. With the exception of maybe Titans RB Chris Johnson, there is not another runner in the NFL as field-fast as Spiller, and he will change games out of the gate upon his arrival. His draft value could be affected by two factors — he is not built to be an every-down back, and durability issues have lingered throughout his career and could keep him from ever being more than a dynamic complementary back. However, he will change games for a creative offensive coordinator who knows how to maximize his talent and can be a big-play maker in multiple phases.

2. Charles Scott, LSU
5-11 1/8e, 231e, 4.6e

Scott has not made the same impact as a senior as he did a year ago, not seeing as many carries in a solid backfield, but he does have great size and can factor as a complementary, short-range inside runner. Evaluators have not been enamored with his mushy body or lack of foot quickness, as he lacks the long speed to go the distance and too often stays bottled up and goes down on first contact. However, he will drive his legs through contact and flashes enough strength and power to at least earn a backup job.

3. Montario Hardesty, Tennessee
5-11e, 215e, 4.55e

A career backup who has been slowed by a history of leg and knee injuries throughout his time in Knoxville, Hardesty added some bulk and has emerged as a senior under coach Lane Kiffin. He appears to have lost a gear that he had when he entered the program and lacks long speed and burst, but he is well-built with good musculature. He battles and scraps for extra yardage and plays physical, not shying from contact. He is a capable catcher who might take some time to make his mark in the pro game, but he possesses the competitiveness to become a functional runner in the pros.

4. Toby Gerhart, Stanford
6-0½e, 235e, 4.6e

Gerhart has proven to be a workhorse for Jim Harbaugh, getting nearly 25 carries per game, competing very hard and drawing comparisons within the program to former Stanford great Tommy Vardell. He might possess a similar type of build as Vardell with a strong lower body and a thick, solid frame, but like Vardell, he might have to line up as a fullback or one-back in the NFL, lacking the quickness desired as a tailback in the pro game. His upright running style and limited lateral agility also could make it difficult to stay healthy, which could limit his draft value, as could his continued flirtation with a baseball career.

5. Chris Brown, Oklahoma
5-10½e, 205e, 4.6e

Splitting time with junior DeMarco Murray, Brown has not even been a full-time starter in a talented backfield on a perennial national-title-contending team, and he might never be one in the pros, either. For an undersized back, he is not overly elusive and lacks great strength and power. However, he runs low to the ground, has a knack for finding creases and catches the ball very well. As a complementary role player in a similar mold as Kevin Faulk, he could prove to be a valuable third-down contributor.

UNDERCLASSMEN

1. Jahvid Best, California (Jr.)
5-9½e, 195e, 4.35e

Extremely quick and productive from the time he arrived at California, Best is a darting, undersized runner capable of taking the corner and zigzagging through defenses. He knows how to set up runs and string moves together to elude tacklers, showing outstanding balance and gear change to slice through defenses. He has not missed much time throughout his three-year career and is a great competitor, but his body has taken a beating, and he could wear down more easily in the pros. He will need to split carries with a bruiser and factor in the return game to maximize his talents and preserve his body.

2. Jonathan Dwyer, Georgia Tech (Jr.)
5-11½e, 245e, 4.5e

After beefing up in the offseason, Dwyer has not looked as quick or effective toting the rock this season as he did a year ago, but he has come on strong in recent weeks, rushing 22-186-3 against Vanderbilt and barreling over tacklers. He still must prove to evaluators that he is more than a product of Paul Johnson's triple-threat option offense, which has helped pad his statistics, and that he is more than a one-cut, zone runner and that his weight will not be an issue. However, similar to Beanie Wells a year ago, he has the physical tools to be a bruiser in the pros and could be the top big back in the draft if he declares.

3. Ryan Mathews, Fresno State (Jr.)
5-10½e, 220e, 4.5e

Despite questions about facing inferior competition in the Western Athletic Conference, the nation's leading rusher performed well against competitive Wisconsin and Boise State defenses and has put himself on the map the same way Connecticut's Donald Brown did a year ago by carrying the Bulldogs' offense. Mathews has very good size, runs hard inside, has a strong stiff-arm, powerful hips and good contact balance to rip through tacklers and stay on his feet. He has shown big-play ability by finishing runs and can go the distance. He runs a bit upright and is not accomplished as a receiver, but he has shown he can catch it.

4. Kendall Hunter, Oklahoma State (Jr.)
5-8e, 200e, 4.45e

After suffering nagging foot and ankle injuries early in the season, Hunter has missed five games, and his production has significantly fallen off as Keith Toston has taken over the ground game in his absence. Hunter tried to return against Texas last week but left the game after one carry. Durability issues will loom larger if Hunter does not return soon, but similar to Dez Bryant, who has been ruled out for the season, Hunter showed enough in his first two years in the program that he still likely will warrant considerable interest on Draft Day despite not playing. He is not as thickly built as Maurice Jones-Drew or Ray Rice, but he is a similar type of compact, power runner with great instincts and feel for the game.

5. Joe McKnight, USC (Jr.)
6-0e, 190e, 4.45e

McKnight was billed as the next Reggie Bush upon his arrival, and he has produced some similar highlight-reel runs during his career. However, very similar to Bush since he arrived in the NFL with lofty expectations, McKnight has pressed to live up to the hype, having a tendency to be a little too reckless with the ball, putting it on the carpet more than evaluators would like and struggling to carry the offense. McKnight has not been a featured runner for the Trojans, and he cannot be expected to do so in the pros. The quick, agile runner could serve as a good change-of-pace back and multipurpose option.

Next Friday: WR prospects

PFW has launched its brand-new NFL Draft Newsletter series, with the second issue being released later this month. Produced by PFW's player personnel department under the direction of Nolan Nawrocki, the series consists of four information-packed issues. For more info or to subscribe — click here for PDF e-pub or here for print format.