Keeper leagues come in all shapes and sizes, many with different rules and regulations. Some leagues allow you to keep two players, while others require owners to retain an entire roster. Still other formats force fantasy leaguers to choose between keeping a player and losing the round that player was taken in past drafts.
Regardless of the rules, one thing that's static across all formats is the level of value a player achieves from one season to the next. It doesn't take a rocket scientist to know that you should keep Drew Brees, Chris Johnson, Adrian Peterson or Andre Johnson, but what about the players who are coming off monster campaigns? Are these sudden stars just one-season wonders, or can they retain a high level of production into the future? Here's our look at players who proved themselves to be great keepers, and those we project for continued success.
Quarterbacks
Philip Rivers, Chargers (age 28): Rivers proved that his breakout season of 2008 was no fluke, posting a career-best 4,254 yards with 29 total touchdowns in 2009. Rivers will continue to find success and remain a reliable No. 1 option with the end of the LaDainian Tomlinson era and a newfound reliance on the pass in San Diego.
Ben Roethlisberger, Steelers (age 27):Big Ben had a big season in 2009, throwing for a career-best 4,328 yards with 28 total touchdowns. While the Steelers won't abandon the run altogether, it's pretty obvious that this offense has become much more pass-laden. That's good new for Roethlisberger's fantasy value moving forward.
Tony Romo, Cowboys (age 29): Anyone who was worried that the loss of Terrell Owens would hurt Romo's value had their minds put at ease last season. While his average number of touchdown passes per game decreased, Romo did throw for a career-best 4,483 yards and a career-low nine interceptions. He'll remain a strong fantasy quarterback.
Matt Schaub, Texans (age 28): Schaub was finally able to stay healthy for the first time in Houston, and his impressive 4,770 yards and 29 touchdowns proved that he has the tools to make a significant fantasy impact. Schaub is a legitimate keeper in all leagues in an offense that is one of the NFL's most productive units.
Running backs
Cedric Benson, Bengals (age 27): Benson was able to shed the bust label he carried in Chicago, posting career bests across the board in his first full season as the true No. 1 back in Cincinnati. Benson suddenly has quite a bit of keeper value in the age of the backfield committee.
Jamaal Charles, Chiefs (age 23): Charles still finished last season in the top 12 in fantasy points at his position on NFL.com despite starting only 10 games. Charles (who has similar skill sets to Chris Johnson) is a young player with great value in seasonal and keeper formats as the now unquestioned top back in Kansas City.
Ryan Grant, Packers (age 27): Grant put questions about his fantasy value to rest in 2009, posting career bests in rushing yards and touchdowns. Grant should continue to benefit with the help of one of the league's elite pass attacks keeping stacked fronts to a minimum.
Shonn Greene, Jets (age 24): Greene showed signs of becoming a fantasy superstar down the stretch, posting a combined 263 yards and two touchdowns in the team's first two playoff contests. I'd expect the talented Greene to take over a bigger role in the offense sooner rather than later as Thomas Jones is getting up there in age.
LeSean McCoy, Eagles (age 21): While McCoy still needs to improve on parts of his game, it's hard to look past his potential in an offense that fits his skill set to a T. He is comparable to Brian Westbrook as a runner and receiver out of the backfield, and McCoy has the sort of upside that's very attractive for keeper-league owners.
Rashard Mendenhall, Steelers (age 22): Mendenhall showed off the skills that made him a prominent running back in the 2008 NFL Draft class, posting 1,108 rushing yards and eight total touchdowns. Mendenhall is now the top runner on the Steelers depth chart and a great keeper with a solid value if you lose the round of the players you retain.
Knowshon Moreno, Broncos (age 22): One of the more well-rounded, young runners in the NFL, Moreno seems destined to take on a greater role in the Broncos offense in 2010. The Georgia product is almost certain to make a big future splash in fantasy football with the tools to post around 40 receptions and 1,500-plus scrimmage yards.
Ray Rice, Ravens (age 23): Rice went from being the third option in a backfield committee as a rookie to an absolute fantasy star in his sophomore season, putting up an incredible 78 receptions, 2,041 scrimmage yards and eight total touchdowns. His age and skill set makes him a perfect keeper, especially in leagues that reward for catches.
Jonathan Stewart, Panthers (age 22): Stewart proved last season that he can be a featured back at the NFL level. With DeAngelo Williams out, he rushed for 440 yards and three touchdowns in his last three games. Stewart will continue to share carries in the short term, but his future in Carolina is bright as Williams is slated to be a free agent after the 2010 season.
Beanie Wells, Cardinals (age 21): Wells was basically non-existent from a fantasy perspective during the first half of his rookie season, but the Ohio State product showed flashes of brilliance down the stretch. Wells is a virtual lock to improve on his 2009 totals as the Cardinals will likely run more after the retirement of quarterback Kurt Warner.
Wide receivers
Miles Austin, Cowboys (age 25): A preseason super sleeper on NFL.com, Austin made good on his chance at a prominent role last season with 81 receptions, 1,320 yards and 11 touchdowns. Austin is a great keeper value if you lose the round of the players you retain as he has become the top option in the Cowboys' offense.
Michael Crabtree, 49ers (age 22): Crabtree still posted very good numbers as a rookie despite not participating in training camp or the preseason due to contractual issues. The Texas Tech product has a ton of potential in an improving 49ers offense, so look for his overall numbers to continue to increase over the next several seasons.
DeSean Jackson, Eagles (age 23): Jackson has become one of the most explosive wide receivers in the NFL. He posted career bests in yards and touchdowns last season, and the sky's the limit in an offense that leans on the pass under coach Andy Reid. Jackson is a high-end No. 1 fantasy wideout and should be retained in almost all leagues.
Vincent Jackson, Chargers (age 27): Jackson is a big athletic receiver entering the prime of his career and he put up his best numbers at the NFL level in 2009. Jackson will continue to see more than his share of opportunities to produce and will remain a viable No. 1 fantasy wideout as the Chargers shift from a running to a passing offense.
Sidney Rice, Vikings (age 23): Rice broke out in his third NFL season, posting career bests across the board and becoming an attractive No. 1 fantasy wideout. The one downfall with Rice, and it's a big one, is that his value is closely tied to Brett Favre. Rice will be hard pressed to duplicate his 2009 totals again if Favre retires.
Steve Smith, Giants (age 24): From a fantasy perspective, the "other" Steve Smith is now the one in Carolina. The Giants' Smith was a PPR monster in 2009, posting 101 catches for 1,220 yards and seven touchdowns as the top option for Eli Manning. The USC product has become a nice option in an offense that's leaning on the pass more often.
Tight ends
Brent Celek, Eagles (age 25): Celek became a reliable and productive option for Donovan McNabb in 2009, posting career bests across the board and becoming a top-notch No. 1 tight end in fantasy circles. Celek should continue to be a very attractive option for owners in both seasonal and keeper leagues.
Owen Daniels, Texans (age 27): Owners in deeper leagues should monitor the offseason status of Daniels, who is coming back from reconstructive knee surgery. Remember, he was the top tight end in fantasy football for the first seven weeks of last season before going down with the ailment, so he has the tools to make a serious impact.
Vernon Davis, 49ers (age 26): Davis turned into an absolute steal in fantasy leagues last season. Davis finished as the top tight end in fantasy football despite an average draft position (ADP) that had him coming off the board in Round 13. Whether you lose the round of the players you retain or not, Davis has become a very nice choice.
Jermichael Finley, Packers (age 22): Finley still put up career bests across the board last season even though he started just 10 games and missed three because of injuries. His success down the stretch made him a legitimate fantasy starter, and I think he's on the verge of a breakout campaign. Finley is worth a look in deeper keeper leagues.
Michael Fabiano is an award-winning fantasy football analyst on NFL.com. Have a burning question for Michael on anything fantasy football related? Leave it in our comments section or send it to **AskFabiano@nfl.com**.