I was comparing the QBs the 49ers had last two seasons. I decided to look at their expected points added, as it is a good play-by-play efficiency stat that is accessible. For the uninitiated, it is based on the points expected in the drive before and after the play, based on distance, down, and time left. I considered passes, sacks and dropbacks (passes+sacks). Penalties were not included. This includes Brian Hoyer, C.J. Beathard, Jimmy Garoppolo, and Nick Mullens.
Dropback EPA | dropbacks | EPA/dback | Sack% | Sack EPA | Sacks | Sack EPA/play | Pass EPA | Passes | Pass EPA/play | |
Hoyer 17 | -20.05 | 221 | -0.091 | 7.2% | -31.22 | 16 | -1.95 | 11.17 | 205 | 0.054 |
Beathard 17 | -40.70 | 243 | -0.167 | 7.8% | -36.19 | 19 | -1.90 | -4.51 | 224 | -0.020 |
Garoppolo 17 | 67.51 | 186 | 0.363 | 4.3% | -12.43 | 8 | -1.55 | 79.94 | 178 | 0.449 |
Garoppolo 18 | 1.80 | 102 | 0.018 | 12.7% | -19.88 | 13 | -1.53 | 21.68 | 89 | 0.244 |
Beathard 18 | -12.46 | 186 | -0.067 | 9.7% | -42.93 | 18 | -2.39 | 30.47 | 168 | 0.181 |
Mullens 18 | 42.17 | 291 | 0.145 | 5.8% | -29.58 | 17 | -1.74 | 71.75 | 274 | 0.262 |
Beathard 17-18 | -53.16 | 429 | -0.124 | 8.6% | -79.12 | 37 | -2.14 | 25.96 | 392 | 0.066 |
Garoppolo 17-18 | 69.31 | 288 | 0.241 | 7.3% | -32.31 | 21 | -1.54 | 101.62 | 267 | 0.381 |
Now a few observations.
Lack of OL continuity hurt us a lot, especially with Weston Richburg playing injured the whole season.
CJB improved significantly in a year.
The Sack EPA difference is probably due to 3rd-down plays. The "yards lost/sack" (not shown here) was similar for the four QBs, all highest quartile (7-7.6 yards/sack), except of CJB 2018 (8.6 yard/sack, league worst in the past season).
Pure passing efficiency was almost the same for the three 2018 QBs. The main difference is the sack% (I blame the OL).
Including DPIs would boost CJB's ad JG's passing numbers.