The Lions are ranked 25th in the NFL against tight ends according to Football Outsiders.  Overall, their pass defense (6th overall) ranks just slightly above the 49ers, but Detroit falls off quite a bit in the tight end category.

Here are the Lions vs. tight ends over their first five games:

TB: Winslow (6 receptions for 66 yards)
KC: Pope (2 receptions for 9 yards)
MIN: Rudolph (3 receptions for 39 yards) and Shiancoe (1 for 8; TD)
DAL: Witten (8 receptions for 94 yards; TD), Bennett (2 for 22), and Phillips (3 for 8)
CHI: Davis (3 receptions for 25 yards; TD) and Spaeth (1 for 8)

According to both Football Outsiders’ DYAR and DVOA rankings, the Lions have yet to face a tight end as good as Vernon Davis, and have only faced one as good as Delanie Walker (which was Witten, who had a great game against them).

Also, according to those same rankings for the quarterback position, the Lions have only faced one quarterback better than Alex Smith (Tony Romo, who successfully managed to get the ball multiple times to three of his tight ends).

Alex Smith has done a great job so far this year of spreading the ball around, and Davis and Walker top that list in terms of touchdowns (5 of 7 have gone to them).  Coach Harbaugh and OC Greg Roman have increasingly succeeded at creating successful game plans against the opposing defense.  These things, put together with the weakness the Detroit Lions have had thus far in covering tight ends, may create a potential great day for both Vernon Davis and Delanie Walker.

Detroit is also ranked 24th against non-#1-or-#2 receivers, which means if Kyle Williams was going to step up, this Sunday would be a good day to do it.  If the Lions over-plan for San Francisco’s tight ends, Williams (or even Crabtree, Ginn) will be next in line for an awesome day.