They're used, abused and tossed aside for younger, cheaper models. Happens all the time.
And that's what's happening with Ryan Grant.
Grant turned 29 in December. He took a pay cut before last season and was overwhelmingly the Green Bay Packers' best running back during the second half of a 15-1 campaign.
His thank you?
Apparently, it's thanks for the memories.
Grant is a free agent. The Packers are deep at running back, but the depth chart doesn't boast much in the way of proven, productive talent. Yet, the Packers have shown practically no interest in re-signing Grant, with a source telling Packer Report on Friday that it's "unlikely" the franchise's No. 5 career runner will return to the team.
From one perspective, the Packers' stance is understandable.
A few years ago, ESPN.com's Tristan Cockcroft did a study linking running backs' performance to age.
Looking at the top 50 rushers in NFL history, they averaged 1,307 rushing yards, 1,660 total yards and scored 10.9 total touchdowns when they were 25 years old (ages as of Sept. 1 of each season). It was downhill from there. Backs who were 28 and 29 averaged 1,188 rushing yards, 1,495 total yards and 9.9 total touchdowns. Then came the big three-zero, when those backs averaged 1,000 rushing yards, 1,101 total yards and 6.6 total touchdowns.
A separate (undated) study by Pro-Football-Reference.com showed that 62 percent of running backs were less productive when they were 29 than when they were 28.
The other perspective, however, is worth considering.
Last season, James Starks rushed 133 times for 578 yards (4.3 average) while Grant rushed 134 times for 559 yards (4.2 average). Starks caught 29 passes for 216 yards (7.4 average) while Grant caught 19 passes for 268 yards (a 14.1 average buoyed by his 80-yard touchdown).
Put it together, Grant finished with 827 total yards and averaged 5.4 yards per touch while Starks finished with 794 total yards and averaged 4.9 yards per touch.
Moreover, during the second half of the season, Grant carried 73 times for 314 yards (4.3 average) in eight games compared to 37 rushes for 138 yards (3.7 average) for Starks, who was limited to five games by injuries.
Injuries are a major issue. Starks hasn't played anywhere close to a full season since 2008 and Alex Green, a third-round pick in 2011, is coming off a torn ACL. Green is ahead of schedule with his rehab, but can the Packers really count too much on a player who got just four touches as a rookie? The other option is Brandon Saine, an undrafted free agent in 2011 who got 33 touches as a rookie.
In that light, the Packers are taking a huge gamble by giving Grant the cold shoulder. At about $9.3 million under the salary cap, it's not like they couldn't afford to give him a minimum contract enhanced with incentives.
Is Grant what he was in 2008 and 2009, when he had back-to-back seasons of 1,200-plus yards? With his history of plowing into defenders, probably not, but at this point, he's much more of a sure thing than the running backs under contract.
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Bill Huber is publisher of Packer Report magazine and PackerReport.com and has written for Packer Report since 1997. E-mail him at email@example.com, or leave him a question in Packer Report's subscribers-only Packers Pro Club forum. Find Bill on Twitter at twitter.com/PackerReport.