It might be debatable just how much of an actual sleeper Rashad Jennings is. I think he still qualifies as a sleeper because he has yet to be given the opportunity to show his full potential. He was the backup in Jacksonville for four seasons before signing with the Raiders last off-season and when he was given the ball, he was every bit the workhorse the Raiders needed him to be.
Even still, right or wrong, he is not considered by most to be a viable number one guy. And that opinion will only change when he can sustain a high level of play over an entire season as a feature back. If he re-signs with the Raiders, he will be given that opportunity. And I expect he will make the most of it.
Jennings will be 29 years old in March but the rule of the 30-year-old running back doesn't really apply to him. That rule is typically applied to a back who has been getting 20+ carries a game over most of his career. For instance, Ladainian Tomlinson when he hit 29 had averaged 338 carries per season (21 carries per game) over 7 NFL seasons. Nearly the equivalent of the total number of carries Jennings has had over his entire five-year career (387).
Jennings also takes very good care of his body so he is great shape. His 4.5 yards per carry average last season was far better than Darren McFadden (3.3 yards per carry) had had with essentially the same offensive line over the past two seasons. And his 733 rushing yards was a number McFadden had surpassed just once in his five-year career in Oakland.
Next season the Raiders offensive line should show even greater improvement. He had 1000-yard season numbers last year but he was only the starter for half the season. There is little doubt he could not only duplicate that success but improve upon it with another year in the same offense and an improved line. Even with a couple of expected newcomers taking some carries from him.