When filling out your fantasy football roster, a healthy mix of rookies and veterans is a good idea. Leaning heavily to one side of the age spectrum can be detrimental to success. Sure, those fresh faces look exciting. But remember, it takes awhile for college kids to adjust to the faster pro speeds and they traditionally tire by season's end (Jets RB Shonn Greene admitted to losing steam at the end of his '09 rookie campaign ).

As for football's redwoods, they have unmatched experience and proven toughness. Look at RB Thomas Jones, who recorded back-to-back seasons of 1,300 rushing yards and 13 TDs after turning 30. However, that's not the norm as backs typically decline in productivity as they enter their 30s. Meanwhile, receivers tend to lose their fifth gear the older they get. Aging players are also more susceptible to injuries.

To help answer your young and old questions, here are a few predictions for the '10 season:

Who will be the top rookie RB: Ryan Mathews (age 22), Jahvid Best (21) or C.J. Spiller (23)?

Everybody is raving about Mathews, the Fresno State product who inherited San Diego's feature back role from RB LaDainian Tomlinson. I'm surprised he's sneaking into the first round of many fantasy drafts, even though he hasn't rushed for a single meaningful yard in the NFL. I doubt he'll live up to those lofty expectations. Owners should be happy if he can come close to Tomlinson's rookie numbers (1,236 rushing yards and 10 TDs).

For overall value, I'd wait a few rounds for Detroit's Best. If he can stay healthy (a big "if" given his track record at Cal), he'll be a major weapon in a budding Lions offense that includes gunslinger QB Matthew Stafford and field stretcher WR Calvin Johnson.

In Buffalo, Spiller has made the most of his chances this preseason with RB Fred Jackson recovering from a fractured hand and RB Marshawn Lynch attempting to get the gleam back in his golden teeth. I like Spiller's game-changing ability, but I'm not crazy about the Bills porous offensive line.

Decision time: Best, especially in PPR leagues

Who will be the top rookie WR: Dez Bryant (age 21), Mike Williams (23), Dexter McCluster (22), Golden Tate (22) or Demaryius Thomas (22)?

Bryant, the second receiver selected in the '10 NFL draft, joins one of the league's top passing offenses with QB Tony Romo, WR Miles Austin and TE Jason Witten. He'll likely outplay anemic WR Roy Williams this year but that's not saying much. I'm wary of Bryant's durability, having missed his final collegiate season at Oklahoma State due to an NCAA violation and sitting out this entire preseason due to an ankle injury.

The Chiefs will use Ole Miss speedster McCluster all over the field, including on special teams and in the backfield. As a pure receiver though, it will be awhile before he develops into a threat. Tate has the flashiest name of this bunch and his value got a boost when the Seahawks cut WR T.J. Houshmandzadeh but he's still stuck behind two other receivers on the depth chart. I'm also not a fan of past-his-prime QB Matt Hasselbeck. Thomas, selected ahead of Bryant in this year's draft out of Georgia Tech, has major talent but he's competing for catches in an unproven Broncos offense.

That leaves Tampa Bay's Williams, who has won over coaches and QB Josh Freeman with his work ethic this preseason and outplaying the more-hyped rookie WR Arrelious Benn. Williams is the clear No. 1 receiving threat on a Bucs team that will play from behind a lot this season.

Decision time: I'd rather take a late-round flier on Williams rather than burn a mid-round pick on Bryant. McCluster is another guy you can get cheap who has the most value in leagues that count return yards.

Who will be the top veteran RB: Jones (age 32), Tomlinson (31) or Clinton Portis (29)?

Jones had the best '09 season of this group but he was running behind the Jets solid offensive line. It won't be as easy with a suspect Chiefs line and he'll be overshadowed by the more-explosive RB Jamaal Charles. Tomlinson replaces Jones in New York, where he'll share carries with Greene. L.T. is trying to prove last season wasn't a sign of his demise: for the first time in his career, he failed to rush for at least 1,000 yards and 10 TDs.

In Washington, new head coach Mike Shanahan likes to run the ball, a positive for Portis. However, health is a major concern here as he only played eight games in '09 (494 rushing yards and one TD). RB Larry Johnson is also in the mix.

Decision time: I suspect Tomlinson will outplay Greene at certain times this season and vulture enough goal-line scores to make him the most fantasy relevant.

Who will be the top veteran WR: Hines Ward (age 34), Donald Driver (35) or Derrick Mason (36)?

Most fantasy owners don't like old receivers, overlooking most of them on draft day for a younger commodity. Ward is getting bypassed by his 24-year-old teammate WR Mike Wallace even though he's coming off consecutive seasons of 1,000 receiving yards and six TDs. In Green Bay, Driver has reached the 1,000-yard landmark the past six seasons yet WR Greg Jennings and TE Jermichael Finley are getting more attention.

In Baltimore, the senior of this group, Mason, has been a fantasy asset eight of the past nine seasons. He's in a good situation in '10 with QB Joe Flacco maturing and the Ravens becoming more of a passing team. Still, I'd be surprised if his numbers don't take a hit with the additions of WR Anquan Boldin and Houshmandzadeh.

Decision time: I like Ward the most, especially after QB Ben Roethlisberger returns from suspension. Driver is a close second in that great Packers offense.

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