Losing Keenan Allen for the season is obviously a gigantic blow to the Charger offense - an offense that hasn't proven it can adapt; that it can produce without its best players all at 100%. The change in offensive production was clear to the eye after Allen went down, but let's take a deeper look.
EPA = Expected Points Added. Successful play = 40% of yards needed for 1st down, on 1st down, 60% on 2nd, & 100% on 3rd & 4th. Note: I counted Rivers "run" as a pass play, given that it was a scramble from a pass-drop-back.
No matter what efficiency metric you look, at the Chargers offense went from flat out dominant with Allen on the field, to sluggish at best. (Had the defense not simultaneously collapsed, the 18 point lead may have been enough to win...but we all know how that turned out). In both the run and pass game the offense failed to convert first downs (going from a 1stD every 2.1 plays, to every 4.8 plays) or even set themselves up for first downs (with successful plays almost 30% less often, in the second half). One stat could summarize the frustrating contrast by itself: the Chargers punted ZERO times before Allen went down (almost an entire half), 5 times after the injury.
One aspect I'd like to spotlight - one getting a lot of attention but perhaps not the most accurate representation, is the run game in each half. Gordon & Woodhead's carries by half are as follows
One thing I've heard a lot is that the Chargers abandoned the run game. The pass% in the original table and the numbers in this one show that that is not the case. What is clear is that the run game became much less efficient. Notably, Melvin Gordon was much less efficient. (Woodhead's efficiency dropped, but it was still pretty good in the 2nd half). He rushed only 2 times less in the second half, but averaged almost 2 yards per carry less, and was successful over 40% less. Granted, his 8 1st-half carries were 26.7% of total plays, while his 6 in the 2nd were only 15.8%, but overall there was a higher percentage of runs in the 2nd half - just more by Woodhead, who was rushing more efficiently then.
Upon a quick examination of Gordon's 14 carries, there didn't seem to be any relationship between the personnel/formation and whether Gordon had a successful run (interesting to note - Gates was only on the field for 2 of his 14 runs, both the TDs, in a 6-OL goal-line package). Perhaps the blocking slipped in the 2nd half? (The (raw) Adjusted Line Yards did slip from 3.7 to 3.4). Did Allen's absence allow KC to commit extra attention to the run-game? Regardless, it doesn't seem like running Gordon more would have saved the team from the collapse they suffered. The loss of Keenan Allen is a great one, and we shall see if THIS will be the time the Chargers can finally adapt to offensive adversity.