I pieced together this short video from available highlights. NFL.com isn't real keen on run defense, so it's shy on anything but Giants backs kicking ass. Nevertheless, though limited in scope, I think it offers a good look at the strengths and limitations of Brandon Jacobs. I included clips of Ahmad Bradshaw for comparison and to control for offensive line and play calling. You'll notice the first clip is Bradshaw.
Ahmad Bradshaw's Loose Upfield Cut
Toss play left. Bradshaw moves outside, plants and runs a looping cut up field. Bradshaw is more agile than Jacobs and sometimes it's to his detriment. Bradshaw runs for a good gain, but is slow into the second level.
Clips 2 & 3
Brandon Jacobs' Driving Upfield Cut
In the next two clips, you can see Jacobs driving into the second level with an efficient, powerful cut up field. Jacobs is fastest and strongest when his shoulders are parallel to the goal line. Jacobs has excellent feet and can cut well, but when in motion, his cut range becomes much more narrow.
Clips 4 & 5
Bradshaw's Quick Lateral Cut
Two perspectives on the same run. Here's where Bradshaw has it all over Jacobs: a high speed, lateral cut. Bradshaw is above average cutting "against the grain" on the move, and that cut, coupled with his balance helps him break a long run in the open field.
Jacobs' Narrow Cuts on the Run
This run examples an ideal Jacobs' rush: north to south. A few things are evident. First, his strong second gear, but also the negligible difference between his second and third gear. Jacobs has great burst on the second level, but he won't outrun a DB. More importantly, notice Jacobs' limited cutting range on the move. Some of this is simple momentum, 260 pounds is hard to stop -- even for Jacobs. Jacobs ran a 4.56/40, but a 7.53 three cone drill. The latter is linemen country. Offensive. Jacobs has excellent feet and is no doubt more agile than a linemen, but has limited cutting ability when running downhill. His cuts, sharp and assertive approaching the pile, become restricted and narrow when he's running hard.
Jacobs is a powerful, quick downhill rusher with incredible feet for his size, but his cuts become narrow and deliberate on the run. That's where I think Seattle's gang tackling, penetrative defense will shine. Jacobs is not strong at cutting laterally. His best cuts are up field. If Seattle should get early penetration, Jacobs is poorly fit to cut back away from defenders or scramble for daylight. Jacobs lack of elusiveness should allow Seattle to get bodies on him, and that should negate his power. I have all the respect in the world for Jacobs and think he's a top flight running back, but I see this matchup in Seattle's favor. Their run defense, already dominant, should turn Jacobs into a non-factor.