Matt Waldman’s Rookie Scouting Portfolio showcases why Detroit Lions running back LeGarrette Blount continues eluding the label of “plodder.”  LeGarrette Blount ran a 4.7-second, 40-yard dash and a 4.49-second 20-yard shuttle. When it comes to speed and acceleration grades in the Rookie Scouting Portfolio, both performances are reserve-caliber metrics for the running back position. Long speed…