THEY HAVE a running back who wants to tackle better.

They have a linebacker who seeks encyclopedic knowledge.

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They have a bull of a nose tackle who wants to be stronger, and a tight end who wants to be the best ever.

Only one of these young players started more than half of this season's games for the Eagles. They are a second tier of young talent overshadowed by second-year players such as quarterback Nick Foles and defensive end Fletcher Cox, who already might have shown their strongest hands.

If the second-class quartet follows its stated offseason agendas, the Birds should have more than a wealth of depth in coming years; they should have an embarrassment of riches.

Already, Chris Polk stole the third-down-running-back job from Bryce Brown.

Already, Zach Ertz is Foles' preferred target.

Bennie Logan's play prompted the Eagles to trade veteran Isaac Sopoaga after eight games.

Perhaps most significantly, after showing marked improvement, and while playing his third linebacker spot in his first two seasons, Mychal Kendricks is ready to make a run at the Pro Bowl . . . if he can stop making mistakes.

To that end, Kendricks will head back to Fresno, Calif., and hit the books. Or, rather, the iPad.

"I'm going to be doing a whole bunch of studying, really. I'll exercise my mind more than anything," Kendricks said.

Kendricks played weakside and strongside linebacker in 2012 as a second-round rookie. He moved inside when the Eagles installed a 3-4 defense last spring, and he flourished. He finished the season with four sacks, three interceptions, four fumble recoveries and 137 tackles, second on the team. There is more to be done.

Kendricks heard about other players who make notes about opponents, who file trends and tendencies until they have shelves of binders crammed with information. He plans to document the entire league.

"I'm going to know the history of the game. I will keep track of movement, in terms of personnel and coaches, going certain places," Kendricks said. "I want to know the schemes they like to run. Knowing the stuff they're comfortable with. Who's in certain positions. Concepts of the game, and how they like to implement it. The types of stuff they take with them."

Kendricks benefited by playing next to middle linebacker DeMeco Ryans the past two seasons. Ryans led the Eagles with 177 tackles this season and captained the defense: made the calls, made the adjustments. After eight seasons playing in both conferences, Ryans' knowledge is nearly encyclopedic. Kendricks wants to catch up by watching video.

"That's what I should spend my time doing. Nothing changes that much in this league," he said. "I know my physical attributes have always been there. Your mind always needs growth. You can only get so fast and so strong, but you cannot stop developing your mind. It's a more powerful weapon than anything else."

Unless, of course, you lack power.

That's what Ertz discovered in the first few weeks of his professional career. The Eagles already were well-stocked at tight end with starter Brent Celek and free agent James Casey, and they needed help in the defensive backfield and on the defensive line . . . but they could not resist taking Ertz with the 35th overall pick. He was an All-American out of Stanford, stood 6-5 and weighed 250 pounds; nearly the same size as Celek, who is 6-4 and 255.

Celek, however, is a chiseled fitness maniac, a committed blocker and a monster after the catch. It was Celek's strength advantage that kept Ertz on the sideline much of the 2013 season. Of his 39 catches (including the playoffs), 25 came in the final nine games, as did all four touchdowns.

In a few months, expect Ertz' 250 pounds to be a little less doughy.

"I want to get stronger, be on the field for more plays," Ertz said. "When I've been on the field I think I showed I can make plays and help the team win. I want to be one of the best tight ends in the game, if not to ever play the game."

Certainly, in Chip Kelly's offense, Ertz will be a frequent target, especially if Foles continues to be the quarterback. The pair developed an obvious chemistry while working on the second team early in the season. When Foles became the starter, Ertz became a bigger part of the offense. Both bided their time.

"The thing I was most pleased with was my ability to be patient," Ertz said. "You set all the records for tight ends at your school, and you're picked high, then you come here and you're just another guy . . . but I knew the playing time was going to come, my playmaking ability was going to show through. My time was going to come. And it did. I think it will increase in the future."

Logan's playing time can hardly increase. After supplanting Sopoaga at midseason, Logan was on the field for more than half the defensive plays. That is a high rate of inclusion for a nose tackle on a team that uses designer pass rushes. Still, if he can prove to be more of a bulldozing force up the middle, he could become indispensable in obvious passing situations.

"I could become an impact player," said Logan, a third-round rookie. "There's a lot of improvement and growth I have to do before I get to that level. More upper-body strength, especially. Coming from college, I'm not used to this long of a season."

Logan finished the season at 307 pounds. He wants to finish 2014 at 320 or so.

Polk, 5-11 and 222, wants to go the other way.

"I'll definitely be trying to get faster, more lean," said Polk.

That is a intriguing image.

Lingering shoulder issues caused Polk to go undrafted out of Washington in 2012. He made the Eagles' roster as a free agent, but shoulder and toe injuries limited Polk to seven games as a rookie, in which he never got a carry. So, he had to convince Kelly and his staff to keep him for 2013. They're glad they kept him.

He was a special-teams staple, which was fine, but he showed flashes of brilliance as a ballcarrier.

He touched the ball 15 times in 2013; 11 runs, four catches. He gained 159 yards, an average of 10.6 yards per touch. He scored three touchdowns, including a 38-yard run that sealed the win over Detroit.

However, Polk will return to play behind LeSean McCoy, the most dynamic back in team history. Polk knows how to keep getting a paycheck.

"Blocking. Blocking is definitely attitude. It's almost like a fistfight. You're not going to go in with your hands down. You're going to want to score first. Put your face on him, move your feet, and hopefully the quarterback throws it in time. Those are some big guys, rushing," Polk said. "And definitely I'll work on tackling, for my special-teams play. The fundamentals. Keeping your head up, wrapping up, not overpursuing the ball."

McCoy remains a deficient blocker. Brown, talented but raw, was McCoy's main backup.

That still gave Polk enough playing time on third downs to impress. He rushed for 4,049 yards and hit the 100-yard mark 21 times in his three seasons at Washington, which, without the shoulder injury concerns, might have made him a second-round pick. If given the chance, Polk has the pedigree and polish to make a serious impact.

None will progress without offseason effort.

Ertz said he will probably stay in Philadelphia and immerse himself in the sports science program. Logan said he might return to Houston, where he trained for the NFL draft combine at a CES Performance site. Polk is from Redlands, Calif., a few hours from Fresno. Guess who he will be spending his offseason with?

"Me and Kendricks train a lot together in the offseason," Polk said.


Maybe Kendricks will come back leaner and faster.

Maybe Polk will come back smarter.

Either way, it couldn't hurt.

On Twitter: @inkstainedretch