Not to be a contrarian, but look at the teams San Diego's D has faced. KC, Jax, Ari, Oak, Sea, StL. Any of those teams have a really potent aerial offense? Sam Bradford was arguably the best QB they've faced this season.
The D's numbers are dubious at best.
Offenses
---------
ARZ: Pass 153 (30th), Run 087 (29th), Total 240 (31st), Pts 18 (25th)
SEA: Pass 207 (21st), Run 086 (30th), Total 292 (27th), Pts 20 (20th)
JAX: Pass 165 (26th), Run 147 (3rd), Total 312 (22nd), Pts 21 (15th)
OAK: Pass 182 (23rd), Run 130 (10th), Total 313 (21st), Pts 20 (18th)
STL: Pass 211 (19th), Run 104 (17th), Total 315 (20th), Pts 17 (28th)
KC : Pass 164 (27th), Run 165 (1st), Total 329 (18th), Pts 22 (14th)
NE : Pass 231 (14th), Run 123 (12th), Total 354 (10th), Pts 30 (1st)
As for the pass defense, Carolina, Oakland and Buffalo are all top 10 pass defenses while the Pats, Steelers, Falcons and Titans are all in the bottom 10 (Jets are just outside at #22).
Here are the stats SD should be concerned about:
Off. 3rd Down Conv: SD 39% (17th), Pats 49% (3rd)
Penalties: SD 38 (19th), Pats 28 (T-9th)
Turnover Margin: SD -3 (26th), Pats +2 (9th)
Kickoff Avg Distance: SD 8 yd line (28th), Pats goal line (2nd)
Avg Punt Return: SD 24 yds, Pats 5 yds
And an interesting bonus stat for SD. Their punting net is only 26 yds while their average gain per play is 6.5...meaning they would only be risking on average less than 20 yards of field position by never punting.