NFC West offenses rank 21st (Seattle), 28th (Arizona), 31st (San Francisco) and 32nd (St. Louis) in third-down conversion rates this season.
I've broken out the conversion rates by play type and quarterback.
For example, the Seahawks' Tarvaris Jackson has 51 successful conversions on 124 pass attempts. His team has rushed for 13 first downs in 33 carries. He has taken 14 sacks. He has gained one first down on six scrambles. That adds up to 65 team conversions in 177 third-down plays when Jackson was quarterback, good for a 36.7 percent conversion rate that leads the NFC West.
The sack numbers jump out. Those are drive-killing plays by definition, but they do not show up in traditional third-down passing stats.
How teams fare on first and second down affects their chances on third down, of course.