there are now stats for team offensive lines.
There's conventional stuff like sacks allowed, sack yards, QB hits, and tackles for losses. But there's also the advanced stuff like run SR, -WPA and -EPA.
I've included run SR because offensive lines are so critical to the first few yards of a run. Once a RB is sprung into the deeper levels of the defense, longer gains are on his shoulders, but until then, it's primarily the line that makes the difference between a 4 yard gain and a 2 yard gain.
-WPA and -EPA are more abstract. The full explanation is here, but this is a brief explanation of how these stats work. It starts with the idea that it's offensive line's job to stop bad things from happening, like sacks, stuffs, short gains, and QB hits. So when bad things like that are done by the opposing defense's front seven, it's usually due to some failure by the offensive line. When negative EPA or negative WPA plays occur at the hands of front seven defenders, the loss of WPA and EPA are attributed to the line. All that WPA and EPA accumulate, and can only be negative, which is why I call the stats -WPA and -EPA.
The average -WPA and -EPA, whether for all games or for the season, is known. So we can adjust -WPA and -EPA to estimate the net WPA and EPA attributable to the offensive line.
In this implementation, offensive lines are not docked due to sacks, hits, or strips due to blitzing defensive backs. Also, plays by linebackers in pass coverage are not counted against offensive lines.
Certainly, -WPA and -EPA are not perfect distillations of offensive lines' performance. Mobile QBs, with quick reads and releases, and elusive RBs would make their lines look better by any measure, just as sturdy lines have always made QBs and RBs look better. There's the fullback to consider in many formations, but frankly, he's almost as much a part of the offensive line as any tackle or guard. On the whole, although far from perfect, I think this is step forward in quantifying how line play affects the game. Its shortcomings are no different than any other football stat. And it puts a focus on players who don't get the attention they deserve.