2018 Offensive Line Continuity Scores

by Vincent Verhei

The two teams at the extreme ends of the offensive line continuity scale last season both played in the NFC West. One of them achieved continuity perfection and went on to play in the Super Bowl. The other went through an unprecedented number of starters and finished with the worst record in the league.

Offensive line continuity scores were originally developed by Jason McKinley in the early days of FO (when FO Almanac was still Pro Football Prospectus) and we have since gone back and calculated it for every team since 1999. The continuity scores are based on three variables: number of starters used; number of week-to-week changes in starting lineups; and the longest starting streak of any one five-man unit. A team can earn a maximum of 16 points in any one category (one point per game), meaning a team that started the same five linemen in all 16 games would get a perfect score of 48; the 2018 Los Angeles Rams last year became the 38th team do so, as the quintet of Andrew Whitworth, Rodger Saffold, John Sullivan, Austin Blythe, and Rob Havenstein started ever game, including the playoffs. (This is no doubt a large reason they were able to post the highest adjusted line yards of any offense on record.) Hypothetically, if a team started five brand new linemen every week of the year, they would get a "perfect" score of -57, though of course nobody has ever come close to that.

The Rams obviously finish on top of last year's tables in this category, and as you have probably figured out, the Arizona Cardinals are at the bottom.

The most impressive thing about the Rams here is that they were nearly perfect in 2017 too. That year, L.A. had pristine continuity for 15 games before resting starters in Week 17. The most remarkable accomplishment of Sean McVay's Rams is that in 36 combined regular-season and playoff games, not once have they been forced to start an offensive lineman they didn't want to. We'll see how they fare in 2019 without Saffold, who signed with Tennessee in free agency. Continuity scores do not measure offseason personnel moves, but the Rams will be hard-pressed to replace a lineman as reliable as Saffold, who has missed just one game due to injury in the past three seasons.

While the Rams had a heavenly season in the City of Angels, the Cardinals had a hellish year in the Valley of the Sun. By the first week of December, all five of Arizona's projected starters in the preseason had been put on IR or released outright. Even worse, their backups were often injured too, leaving a crew of third-stringers and guys off the street to protect rookie quarterback Josh Rosen as best they could. Here's a look at Arizona's starting offensive linemen in Week 17 against Seattle, and where they had been when the season started:

All told, 13 different players started on Arizona's offensive line last year. That ties the 2007 Rams for the most on record -- and that's not even counting A.Q. Shipley, the projected starter at center who was lost for the year after tearing his ACL in the preseason. The Cardinals have tried to bolster their line with veteran free agents J.R. Sweezy and Marcus Gilbert, but could still use more options here in the draft.

Three teams -- the Detroit Lions, Green Bay Packers, and L.A. Chargers -- tied for the biggest improvements in continuity score in 2018. The biggest decline was suffered by Tennessee, mainly because they used four different starters at right tackle alone.

The Sean Payton Trophy

While most teams and coaches favor continuity along the offensive line, Sean Payton and the Saints have historically been the clear outlier. The 2016 Saints set the benchmark for shuffling pieces around, making 11 line changes with only seven different starters, a ratio of 1.57 changes per starter that is the highest on record. The 2005 and 2017 Saints both made 10 line changes among seven starters, tying them for second place; the 2015 Saints also make the top five. Things switched for the Saints last year though -- despite using ten different starters, they made only eight changes. That's the kind of thing that can happen when you rest three starters in Week 17.

With the Saints line solidified for most of the year, the Sean Payton Trophy goes to the Houston Texans, who made 10 line changes between eight different starters last year. Julie'n Davenport (LT and RT), Martinas Rankin (LT and LG), and Greg Mancz (LG and RG) each started games at multiple positions on the Houston front.

League-wide Trends

League-wide offensive line continuity has been declining for several seasons, and in the big picture that's still true. The average continuity score in 2018 was 29.7, up significantly from 2017's average of 27.9, but still the second-lowest mark in the last two decades.

As you'd expect, offenses that can keep the same five linemen on the field tend to have a lot of success. The correlation between continuity scores and offensive DVOA last season was .440; correlations for passing offense and rushing offense were .378 and .362, respectively. There's a chicken-or-egg effect that drives this correlation from both directions -- teams that suffer a lot of offensive line injuries tend to have poor results on the field, while offenses that play poorly from the start are more likely to bench their starters and promote their backups.