Here's a key matchup to watch in Sunday's Vikings-Lions game.
Vikings QB Donovan McNabb vs. Lions third-down defense
An initial look at the numbers suggests that the Vikings haven't been bad on third downs this season (9-for-22, 11th in the league). But a deeper look shows that when it counts, they aren't as successful, going 1-for-9 on second-half third-down conversions thus far.
Third downs exploit QB Donovan McNabb's weaknesses as a passer. His accuracy on short-and-intermediate throws has been inconsistent throughout his career, which becomes a problem on third down. He's much better when he throws vertically on early downs and creates quick scoring opportunities.
The numbers from his last successful season (2009 with the Eagles) bear this out. Philly was fifth in the league in scoring, but 23rd in third-down conversion percentage. McNabb was seventh in the league in yards-per-attempt that season, proving that the offense was predicated on McNabb's ability to create big plays with the deep ball.
The best way to attack the Lions' defense that has been good on third downs so far this season (eighth in the league, 8-of-25) is to avoid third down as much as possible. While the Vikings don't have the speed on offense that the Eagles had in ’09, the Vikings still have weapons that can stretch the field in Percy Harvin and Bernard Berrian. That way, the Vikings' offense can be in more advantageous situations than it has been in the first two games.