Chase for the Championship Grades

With three races to go in the season, SI.com's Tim Tuttle hands out his grades for the 12 drivers in the Chase for the Championship, beginning with Jimmie Johnson, who has virtually clinched his third straight Sprint Cup title. He has been brilliant in running up an 183-point advantage, using a dynamic combination of speed and smarts for two wins, two seconds, fifth, sixth and ninth in seven Chase races.