FanPost

Ok, but What about the O-line? (A Study)


Issue

In 2018, the 49ers allowed the quarterback to be hit 125 times (2nd most in the NFL) with 48 of those hits resulting in sacks (9th most in NFL). However, no significant moves were made in free agency or the draft to improve the offensive line.

Hypothesis

One reason Shanahan may believe sticking with the current offensive line is the best move is that the offensive line made steady improvement protecting the quarterback throughout the season.

Purpose

The purpose of this study is to review the available data to determine if the offensive line did improve in pass protection over the course of the 2018 season.

Methodology

-Determine the number of quarterback hits and sacks allowed in each game of the 2018 regular season.

-Using the above and the number of pass plays per game (i.e., attempts + sacks), calculate the percent of pass plays that result in a quarterback hit (Hit%) and the percent of pass plays that result in a sack (SK%).

-Next, the quality of each opposing team’s pass rush was calculated similarly to done above, but for the whole 2018 regular season. The opposing team’s 2018 sack rate (D-SK%) and quarterback hit rate (D-Hit%) were calculated using the team’s 2018 total sacks, total quarterback hits, and total pass plays that the defense faced.

-Finally, for each week, the "SK% delta" is calculated by comparing the SK% to the D-SK% and the "Hit% delta" is calculated by comparing the Hit% to the D-Hit%. For example, in week 1, the Vikings got a sack on 8.3% of pass plays. On average in 2018, the Vikings got a sack on 9% of pass plays. Therefore, the SK% delta is -0.7%, which means the 49ers O-line did a little better than average against the Vikings as far as limiting sacks.

Assumption

Sacks and quarterback hits are primarily a result of poor play by the offensive linemen. This assumption will be discussed further at the end of the study.

Results & Discussion

The data used to perform the analysis and the results are shown in Table 1. For each week, the results of interest are as follows:

SK% delta: the difference between the percentage of pass plays that result in a sack of the 49er quarterback (SK%) and the percentage of pass plays that result in a sack for the opposing team’s 2018 season. In other words, if SK% delta is negative, then the 49ers allowed fewer sacks than the opposing defense got on average during the 2018 season. When SK% delta is positive, then the 49ers allowed more sacks than the opposing defense got on average during the 2018 season.

Hit% delta: this is the same as above, but for hits on the quarterback instead of sacks.

Table 1: Week-by-Week Quarterback Protection Performance

49ers Opposing defense stats for 2018 Opp D Stats that week
Week QB Pass Att Defense D-Pass Att D-SK D-SK% D-Hits D-Hits% Sacks SK% QB Hits Hit% SK% delta Hit% delta
1 Garoppolo 33 Vikings 503 50 9.0 94.0 17.0 3 8.3 9 25.0 -0.7 8.0
2 Garoppolo 26 Lions 496 43 8.0 77.0 14.3 6 18.8 8 25.0 10.8 10.7
3 Garoppolo 30 Chiefs 632 52 7.6 105.0 15.4 4 11.8 5 14.7 4.2 -0.6
4 Beathard 37 Chargers 548 38 6.5 85.0 14.5 1 2.6 9 23.7 -3.9 9.2
5 Beathard 54 Cardinals 506 49 8.8 90.0 16.2 4 6.9 9 15.5 -1.9 -0.7
6 Beathard 23 Packers 527 44 7.7 74.0 13.0 2 8.0 4 16.0 0.3 3.0
7 Beathard 27 Rams 533 41 7.1 94.0 16.4 7 20.6 12 35.3 13.4 18.9
8 Beathard 28 Cardinals 506 49 8.8 90.0 16.2 4 12.5 8 25.0 3.7 8.8
9 Mullens 22 Raiders 480 13 2.6 48.0 9.7 0 0.0 2 9.1 -2.6 -0.6
10 Mullens 39 Giants 560 30 5.1 84.0 14.2 0 0.0 3 7.7 -5.1 -6.5
12 Mullens 32 Bucs 534 38 6.6 93.0 16.3 4 11.1 10 27.8 4.5 11.5
13 Mullens 48 Seahawks 546 43 7.3 109.0 18.5 3 5.9 15 29.4 -1.4 10.9
14 Mullens 33 Broncos 549 44 7.4 94.0 15.9 3 8.3 9 25.0 0.9 9.1
15 Mullens 29 Seahawks 546 43 7.3 109.0 18.5 3 9.4 10 31.3 2.1 12.7
16 Mullens 38 Bears 615 50 7.5 100.0 15.0 1 2.6 6 15.4 -5.0 0.3
17 Mullens 33 Rams 533 41 7.1 94.0 16.4 3 8.3 9 25.0 1.2 8.6

For 9 of the 16 games, the opposing defense sacked the 49ers quarterback more times per pass play than the opposing defense’s 2018 average, as shown in Figure 1. The worst week was the first game against the Rams, where Beathard was "beat-hard" getting sacked on 20.6% of pass plays while the Rams defense in the 2018 regular season averaged only 7.1% of pass plays resulting in getting a sack. With the exception of Week 12 against the Bucs, the 49ers performance regarding limiting sacks was improved over the second half of the season.

Figure 1: 49ers Weekly Performance Limiting Sacks

When considering hits of the quarterback, the previously noted late season improvement regarding sacks does not apply, as shown in Figure 2. For 12 of the 16 games, the opposing defense hit the 49ers quarterback more times per pass play than the opposing defense’s 2018 average. Overall, the offensive line’s performance limiting quarterback hits was actually worse after the bye week. This indicates that the late season improvement in limiting sacks was more a result of Mullens being better at avoiding sacks than any indication of improvement of the offensive line.

Figure 2: 49ers Weekly Performance Limiting Quarterback Hits

Conclusions

The pass protection performance of the offensive line did not improve over the course of the 2018 season. Any apparent improvement in limiting sacks over the second half of the season was more a result of Mullens being better at avoiding sacks than Garpoppolo and Beathard, which is supported by hits on the quarterback actually being more frequent after the bye week.

Future Work

As previously mentioned, this study is based on the assumption that sacks and quarterback hits are primarily a result of poor play by the offensive linemen. However, there are several other factors that could affect the number of sacks and quarterback hits, such as: 1) the running back not picking up a blitzing defender, 2) an overload blitz, or 3) a "coverage sack" where the quarterback has to hold the back too long because the receivers could not get open. Future studies may be performed to attempt to determine how many of the sacks and quarterback hits were actually a result of poor offensive line performance. However, such a study would require reviewing video of all 125 quarterback hits. If some sick individual has created a video compilation of all 125 plays that resulted in our quarterback getting hit, please let me know.

References

Pro-football-reference.com

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