Tough running

Frank Gore has overcome bad blocking by using his speed in the open field. Ezra Shaw/Getty Images

This past Sunday night, the Arizona Cardinals' run defense stuffed Adrian Peterson at the line on run after run, allowing him only 19 yards on 13 carries. But that was just an appetizer, because on "Monday Night Football" Darnell Dockett and his buddies get to take on the worst run-blocking line in the National Football League.

"Wait," San Francisco fans might be saying. "We have the worst running game in the league? How can you say that when Frank Gore is averaging 4.9 yards per carry?"

To explain, let me show you a way we can estimate the importance of a running back compared to his offensive linemen. We know that at some point in every long running play, the running back has gotten past all his offensive line blocks. There are initial blocks that open a hole for the first couple of yards. Then there are the "second-level" blocks that open things up for the back to make a big play. Eventually, the running back hits the open field, and at that point the blocking doesn't matter anymore. The runner succeeds solely based on his own speed and elusiveness, compared to the speed and tackling ability of the defensive players.

This basic idea of blocking at different levels translates into a metric that Football Outsiders calls Adjusted Line Yards. We take every run by a running back, and adjust it the following way:

0-4 yards: 100 percent strength

5-10 ("second level") yards: 50 percent strength

11-plus ("open field") yards: not included

Runs for a loss: 120 percent strength