The Patriots right tackle Sebastian Vollmer broke his leg halfway through the 2013 season and was replaced by Marcus Cannon.
The 30-year-old and former 2nd-team-All-Pro tackle Vollmer was just another loss in a season of injuries- and he could possibly have been the most important. The downfall of the Patriots came with poor offensive line play and substituting a player of Vollmer's caliber off a struggling right side of Ryan Wendell and Dan Connolly could only serve to hurt the team.
That's not to say Cannon is a bad player- he played more than admirably- but that any turnover of the best player in a struggling player group will likely lead to more troubles.
Of course, did this actually play out over the second half of the Vollmer-less season?
You might be surprised to find out no, it did not.
According to Pro Football Focus, Vollmer allowed 2 sacks, 1 quarterback hit, and 13 pressures. Cannon allowed 1 sack, 4 hits, and 12 pressures. That's roughly equivalent, even if you argue that the second half gauntlet of the Panthers, Broncos, and Texans was more difficult than any stretch in the first half of the season.
Of course, there's the fallout at right guard and center in protection. One would expect the other blockers on the line to struggle without Vollmer as the bookend.
Except Dan Connolly was consistent with a slash of 2 sacks/4 hits/14 pressures with Vollmer and 1/8/13 without. Wendell was 4/3/13 with Vollmer and 2/4/11 without him.
So perhaps the fall in pass protection from Vollmer to Cannon wasn't as pronounced (although one could definitely argue that Cannon deserves a legitimate attempt at claiming the right guard role). How about run blocking?
I compared the running back committee of Stevan Ridley, LeGarrette Blount, Brandon Bolden, and Shane Vereen to see how they fared with Vollmer and without him. I ignored the runs by James Develin and Tom Brady because there wasn't enough data to compare.
To evaluate the running backs, I used a "success rate" stat that looked at the needed yardage gained by the running back. If a back gained 7 yards on a first and 10, they received a score of 0.7. If they gained 5 yards on a 2nd and 4, they received a score of 1.25. A success on first down was 4 yards or more. Success on second down was at least half of the remaining yards needed for a first down. Success on third or fourth down was picking up the first down yardage.
It turns out that the success rate didn't really change when the Patriots ran to the right. 43.3% of runs to the right with Vollmer were successful, while 46.6% of those runs without Vollmer were successful.
In fact, across the board, success rate were up without Vollmer on the field (albeit a statistically insignificant amount and likely attributed to the complete explosion of Blount over the second half of the season).
With regards to the percentage of necessary yards for a first down, the Patriots actually missed Vollmer over the second half of the season. While the team was better at running the ball to the left during the second half of the season (and that's why you should expect the return of Logan Mankins in 2014), it was slightly better at running up the middle and to the right with Vollmer on the field.
What this means is that Vollmer was better as a run blocker than Cannon, even if it's just a slight amount.
The return of Vollmer will make the offensive line better. His return in conjunction with the continued growth of Nate Solder, the re-emergence of Mankins, and the hopeful regression to the mean of Ryan Wendell will yield a much stronger offensive line than what played in 2013.
This is also perhaps a sign of support for Cannon as a starting player. He earned time last season and the drafting of right tackle Cameron Fleming shows the Patriots believe this will be the last year they'll get out of Cannon. Perhaps it would be for the best if they let him back into the competition to start at right guard.