Green Bay Packers linebacker Julius Peppers (56) runs back an interception for a touchdown in a 42-10 victory over the Minnesota Vikings at Lambeau Field on Thursday night. (Photo: Kyle Bursaw/Press-Gazette Media)

Every once in awhile you have to throw your own book out the window.

So it is with Julius Peppers and his contract next year with the Green Bay Packers.

Branch Rickey, the general manager for baseball's St. Louis Cardinals, Brooklyn Dodgers and Pittsburgh Pirates from 1919 through 1955, was in the vanguard of personnel men in North American sports who developed the modern philosophy of valuing players.

Rickey had numerous sayings regarding team building, and perhaps his most famous was that it's better to part with a player a year early than a year late.

It's a sound approach advocated either explicitly or implicitly through the years by some of the NFL's greatest minds, including Vince Lombardi.

As that saying suggests, Rickey always kept an eye out for players' decline when they hit their later 20s and early 30s. He espoused, in general, fielding young teams.

Ted Thompson, the Packers' general manager, may or may not know anything about Branch Rickey. But in his 10 seasons running the Packers' football operations, he's clearly proven wary of signing older players, even good ones, because of concerns they could decline significantly in an offseason. His teams consistently are among the five youngest in the NFL. He's probably an even stronger adherent to Rickey's views on aging athletes than most NFL GMs, which is no small statement.

Which brings us to Peppers, the 34-year-old outside linebacker Thompson signed as a free agent in March. The signing was uncharacteristic for Thompson, both because Peppers was a marquee player on the open market and Peppers' age.

Green Bay Packers linebacker Julius Peppers (56) celebrates his interception returned for a touchdown with teammates. (Photo: Kyle Bursaw/Press-Gazette Media/@kbursaw)

But the Packers' risk actually wasn't that great. Peppers wasn't exactly cheap at a cost of $8.5 million in salary and bonuses this season, but Thompson isn't committed beyond 2014. The deal is for three years, but the guaranteed pay was $7.5 million, so the Packers if necessary could treat this as a one-year rental, cut Peppers in the offseason and move on without serious salary-cap implications.

However, Peppers has been very good for them. He's not the player he was early in his career at Carolina, but he is every bit the physical freak he appeared to be when the Packers signed him.

His athleticism along with his size (6-feet-7, 287 pounds) are impressive even at 34. Like Charles Woodson before him, he also implicitly commands respect from teammates. That was evident last week when they voted him a captain for the playoffs even though he has introverted tendencies and is in his first year with the team.

Peppers has been one of the Packers' best defensive players this season, probably behind only Clay Matthews. The Packers are getting their money's worth.

But the tougher question is next year, when he'll be 35 and make $9.5 million in salary bonuses ($8.5 million in base salary, $500,000 in workout bonus, and up to $500,000 in per game roster bonuses).

The only Packers player who will make more cash in 2015 is quarterback Aaron Rodgers ($11.6 million). And only two teammates will have a cap number higher than Peppers' $12 million: Rodgers ($18.25 million) and Matthews ($12.7 million).

The Rickey book says the Packers were fortunate to get out of Peppers what they did this year and that they'd be pushing their luck to bring him back in '15 with a $1 million raise. Thompson's history says the same.

But this looks like one of those times Thompson should disregard the book.

Full disclosure, in March of 2013, I thought Thompson should push hard to outbid Atlanta for free-agent running back Steven Jackson. Jackson was old for his position — he would turn 30 later that offseason — but he hadn't shown signs of significant decline, and the Packers' need was acute.

But Thompson drew his line and wouldn't budge when Atlanta went further. He was right. He ended up selecting Eddie Lacy in the draft, and now the Packers have one of the league's best young backs rather than a broken-down 31-year-old who is washed up.

Another great lesson in valuing players.

But Peppers isn't a running back, which is the fastest-aging position in football, and he's a rare enough athlete to be worth risking that $9.5 million next year.

For one, Peppers' play doesn't appear to have declined from last season. He has the same number of sacks (seven) as he finished with in 2013 and has one game to play. Also, according to Pro Football Focus his other pass-rushing and playmaking numbers are about the same: 10 quarterback hits this season to six last year; 26 hurries to 27 last year; three batted passes in both seasons; and 24 stops (defined as a solo tackle that constitutes a failed play for the offense) to 26 last season.

More importantly, Peppers is the exception that tests the rule. He is not the normal 34-year-old NFL player and won't be the normal 35-year-old. He has exceptional size, and he still plays with good flexibility in his legs and hips. He's never had a major injury and has missed only six of 207 games in his career, which also bodes well for longevity.

The Packers have used him a little more than they probably would like — he's played 775 defensive snaps, compared with 851 in 2013 and 785 in '12. But in the last three games, he's had seven combined sacks, hits and hurries, which is about his pace for the season. And last week in more limited playing time (only 31 snaps) against Tampa Bay he had two sacks and a forced fumble. So he hasn't crashed late in the season, as older players often do.

The Packers don't have to decide now, and there's enough football left that something could change. Peppers could get hurt. He could disappear in the playoff games, which would give pause, because the Packers brought him in to make a big play or two in big games.

But Thompson doesn't have much leverage. If he asks Peppers to take a pay cut, Peppers could say, "cut me," and likely have a decent offer waiting in free agency.

The Packers also have the cap room to handle the cost. Based on salary figures at OverTheCap.com and SpoTrac.com, the Packers have committed about $122 million to next year's cap. By cutting linebackers A.J. Hawk and Brad Jones, they'll pick up another $7.25 million. Barring any last-minute contract extensions, they'll also carry over anywhere from $7.5 million to almost $8 million from this year's cap to next year's.

The league has projected the 2015 cap to be as high as $141.8 million, but considering it badly under-projected this year's cap, it's likely that reports are correct in saying a more likely figure is $145 million.

At that number, the Packers will have about $30 million in cap room when the offseason starts. Before thinking that's a huge number, remember they probably will try to retain several of their most notable free agents, a list that includes Randall Cobb, Bryan Bulaga, Tramon Williams, B.J. Raji, Letroy Guion and Davon House.

They also will have a rookie class and might want to sign a free-agent inside linebacker or two.

But Peppers' contract already counts on that $30 million of cap room. They don't need the $7 million in room they'd gain by cutting Peppers to get done what they need done this offseason.

Thompson has shown that valuing personnel by the book pays off. But even Rickey occasionally violated his own principles — second baseman Frankie Frisch played for Rickey's Cardinals into his late 30s. And unless something changes between now and March, Thompson should stick with Peppers for another year, even at $9.5 million. Every once in awhile you have to break the rules.

— pdougher@pressgazettemedia.com and follow him on Twitter @PeteDougherty.