Matt Rourke/Associated Press

The 2014 NFL preseason kicked off on Sunday night, and fantasy football owners understand that it’s time to get serious as draft season approaches.

There are keys and strategies to winning a fantasy championship. Owners must be able to decipher the rankings of the top players and find the unknown NFL sleepers worth late-round selections.

Here are the top unknown sleepers at every position and the top 25 overall players.

Top Unknown Sleepers at Each Position Position Sleepers Quarterback Josh McCown, Tampa Bay Buccaneers Running Back Devonta Freeman, Atlanta Falcons Wide Receiver Jordan Matthews, Philadelphia Eagles Tight End Travis Kelce, Kansas City Chiefs Defense Green Bay Packers Kicker Nate Freese, Detroit Lions Source: Donald Wood's Rankings

2014 Fantasy Football Top 25 Rank Player Bye Week 1 Jamaal Charles, KC 6 2 LeSean McCoy, PHI 7 3 Adrian Peterson, MIN 10 4 Matt Forte, CHI 9 5 Peyton Manning, DEN 4 6 Eddie Lacy, GB 9 7 Jimmy Graham, NO 6 8 Calvin Johnson, DET 9 9 Demaryius Thomas, DEN 4 10 Marshawn Lynch, SEA 4 11 Drew Brees, NO 6 12 A.J. Green, CIN 4 13 Aaron Rodgers, GB 9 14 Dez Bryant, DAL 11 15 Brandon Marshall, CHI 9 16 Arian Foster, HOU 10 17 Julio Jones, ATL 9 18 DeMarco Murray, DAL 11 19 Antonio Brown, PIT 12 20 Doug Martin, TB 7 21 Le'Veon Bell, PIT 12 22 Jordy Nelson, GB 9 23 Alshon Jeffery, CHI 9 24 Rob Gronkowski, NE 10 25 Wes Welker, DEN 4 Source: Donald Wood's Rankings

Sleeper You Can't Afford to Miss: Jordan Matthews, WR, Philadelphia Eagles

The Philadelphia Eagles stunned the NFL when they released top receiver DeSean Jackson and he was signed by the division rival Washington Redskins. While Jackson’s departure stole the headlines, Philadelphia quietly added a player who could become a serious game changer.

The Eagles added former Vanderbilt star and rookie wide receiver Jordan Matthews early in the second round of the 2014 draft.

It will be tough for Philadelphia to replace Jackson’s production (82 receptions for 1,332 yards and nine touchdowns), but Matthews will not be doing it alone. The return of Jeremy Maclin from a knee injury and the continued evolution of Riley Cooper will give Matthews room to learn on the job.

Hometown fans are excited about the addition, but they aren’t the only ones. Chris Wesseling of NFL.com and Zach Berman of The Philadelphia Inquirer both believe the Eagles have a gem with their second-round pick:

With defenses focusing on the players around him, Matthews will use his 6’3”, 212-pound frame to rise above defenders and make big catches. The rookie also has the ability to go over the middle, but it is his innate catching ability that will make him such a valuable target in head coach Chip Kelly’s offense.

Regarding Matthews' fit with the Eagles, Mike Mayock of NFL.com mentioned the individual strengths and overall team advantages heading into 2014:

He'll fit in beautifully in Philadelphia and in Chip Kelly's offense. He makes tough catches. He has a big body. He ran faster than a lot of people anticipated (4.46-second 40-yard dash at the NFL Scouting Combine). The Eagles get Jeremy Maclin back. They have added Matthews and Darren Sproles. This team is going to be the first-, second- or third-leading scoring team in the league.

Quarterback Nick Foles proved last season that he is one of the best quarterbacks in the NFL, and he looks to continue proving people wrong in 2014. The lack of a speedy player like Jackson will hurt the team’s deep passing, but the combination of Matthews and Maclin will find success in the team’s high-tempo passing offense.

With the ability to run crisp routes, the willingness to go up and make tough catches in traffic, and the consistency to become a viable red-zone target, Matthews has the skill and the opportunity to become the unquestioned No. 2 receiver for the Eagles and a serious fantasy threat.

Philadelphia’s high-paced offense is built for fantasy football, and Matthews could be the biggest benefactor from Jackson’s offseason departure.

Look to draft him somewhere in the range of Round 9 through Round 12.

Predicted Stat Line: 70 receptions for 1,100 yards and five touchdowns.

Stats via NFL.com.

Follow @Donald_Wood.