What Changed in the Passing Game: Volume III

Today I want to look back at two areas of concern I noted for Trubisky last off-season: deep passes and performance against good defenses.

Deep Passes

Last year, I noted that Trubisky was really good at short passes (15 yards or less past the line of scrimmage) and really bad throwing the ball deep. I also found that short passing performance tends to be less variable year over year than deep passing, which gave us a reason to be optimistic about Trubisky heading into 2019.

Let’s see how that theory played out in 2019.

A few thoughts:

So much for short stuff being consistent. Trubisky’s completion percentage, yards/attempt, yards/completion, and touchdown rate all plummeted from 2018 to 2019.
Some of the completion percentage can be accounted for by drops (as I have previously addressed), but not nearly all of it on the short stuff. Despite throwing shorter passes in the short stuff, Trubisky completed fewer of them. The end result was an extremely inefficient short passing game.

Looking to the deep ball, we see Trubisky attempted deep passes at a lower rate than in 2018, which is something I suggested he should do last offseason. He still threw it deep at a slightly higher than league average rate, which honestly surprised me. I thought he’d be a bit lower.
Trubisky’s deep completion percentage regressed towards the mean a bit, though it was still well below league average. The much shorter yards per completion mark compared to 2018 suggests he was throwing more “intermediate” deep balls than truly deep shots, which will tend to have a higher completion percentage. Go routes were the Bears’ 2nd most frequently targeted route in 2018, and I’m guessing we saw them used less in 2019 (I’ll know for sure once this data is available after the playoffs). Either way, the yards/attempt mark – which was not particularly good in 2018 – dropped drastically in 2019.

History suggested it was likely Trubisky’s short passing success would carry over from 2018, while his deep ball struggles would regress to the mean a bit. Unfortunately, the exact opposite happened. That’s the problem with statistical predictions. They can tell you what is most likely to happen, but there are still a wide range of outcomes that are possible, and there’s no saying for sure which one will come to pass.

Opponent-Weighted Performance

Another trend I pointed out last off-season was that Trubisky feasted on bad defenses and really struggled against average or better ones. I’m going to set the stage here by pulling up my conclusion paragraph from that article:

“These splits are certainly cause for concern, but I don’t think there’s any need for panic – yet. Last year we saw glimpses of how good he can be, but plenty of reminders of how far he has to go. Now in 2019, the glimpses need to start becoming more of the norm. This is year three as an NFL starter and year two in the same offense with the same targets. Trubisky should be mentally far enough along at this point that he can better handle what a decent defense throws at him, which means we need to start seeing him putting up big performances against more than just terrible defenses.”

Let’s look at the data and see if that came to pass (though you can probably already guess what we’ll find). Like last off-season, stats are split by passer rating the opposing defenses allowed: less than 90 (top 16), 90s (next ten), and 100 or greater (bottom 6). Trubisky had 4, 4, and 6 games against teams in those samples, so this is a fairly decent split of his season as a whole. The table below shows Trubisky’s performance in a variety of metrics, with numbers in parentheses indicating how that compares to the average against those defenses.

A few thoughts:

We see the same general trend from 2018 holds true: Trubisky was better than expected against bad defenses and worse than expected against everybody else. So in that respect, maybe his 2019 really wasn’t that different from 2018 after all. He just had fewer games against cupcakes (4 vs. 5) and more games against tough defenses (6 vs. 4).
It is worth noting, however, that Trubisky was relatively less good (though still quite excellent) against those bad defenses. His completion percentage dropped by over 2%, yards/attempt by over a yard, and he threw far more interceptions. DaBearsBlog reader John F fairly notes that Trubisky had 3 absurdly productive games in 2018 against bad defenses that he didn’t quite replicate in 2019 (3 games with a yards/attempt mark above 10, while his 2019 high was 8.9).
Trubisky’s performance against below average to good defenses was remarkably consistent from 2018 to 2019, except he threw far fewer touchdowns (2.0% vs. 3.7%) and interceptions (1.7% vs. 3.7%) in 2019. This tracks with him generally taking shorter, safer throws in 2019, which led to fewer TDs and INTs overall.

Wrap Up

Based on these data, we can see that there are significant portions of Trubisky’s performance from 2018-19 that actually didn’t change all that much. He consistently struggled against good defenses and feasted on bad ones, and accuracy issues led to an ineffective deep ball in both years. Though the areas of weakness remained, his biggest passing positive from 2018 – efficiency in the short passing game – vanished. Add that to his non-passing strengths (avoiding sacks, running) disappearing, and we’re left with a bad quarterback.

Three years into his career, Mitchell Trubisky remains a talented yet extremely inconsistent quarterback. You can still see flashes of his talent, but at some point he needs to become far more consistent to be an NFL starter. Quarterbacks selected in the top 5 typically get their 4th season (at least the start of it), but at this point the chances of Trubisky becoming that consistently solid player the Bears thought they were drafting are pretty slim.