Vikings signed DE Brian Robison to a four-year contract extension. Robison was set to hit unrestricted free agency after this season. Instead, the Vikings lock up their quietly productive left end. Robison started 31 games between 2011-12, compiling 16.5 sacks, 81 tackles and seven batted passes. So far this year, he's graded out as ProFootballFocus' No. 13 4-3 end out of 49 qualifiers.