He's half way to 28 and heading into his seventh season as an RB.
If you look at most RB's their best years just happened or are this year, then it's all downhill.
If MJD was two-three years youger he'd be worth a big contract, but he's too old now. There are VERY few RB's who continue with pro-bowl level production into their 30's.
Love his fumble stat though.