Johnathan Wood | October 8th, 2018

Now that we’ve seen Mitchell Trubisky play four games under Matt Nagy’s tutelage, it’s time to examine how he’s doing. We’ve seen him play 269 snaps and throw 130 passes, and while that’s still a fairly small sample size, it’s big enough that we can begin to analyze how he’s performing in a variety of situations.

Growth Through Each “Quarter”

Last offseason I looked at Trubisky’s performance in 4-game snapshots, borrowing the idea of breaking an NFL season down into quarters from Lovie Smith. There I found that Trubisky got progressively better in every “quarter.” Since Trubisky has played 4 games this year, he now has 16 in his career, giving him a full 4 “quarters” that we can track. Let’s take a look.

Well that looks pretty good. I said last offseason that, statistically speaking, Trubisky needed to throw more TDs while keeping everything else the same. Here we see that he has managed to throw more TDs, and everything else has stayed the same or improved. That’s good growth to see from a 2nd year QB.

Of course, four games is a small sample size, and this doesn’t look quite as rosy if we remove the Tampa game from the equation. Then his yards per attempt drops to 5.7, TD percentage to 1.9%, and his INT % (2.9%) and sack % (8.0%) both rise a bit higher than they were late in his rookie year.

Through three weeks, the stats suggested Trubisky was actually playing worse than late in his rookie year. That’s not entirely surprising given that learning a new offense often results in a step back at first.

Adding the TB game in there makes this look good, but now the question is whether the TB game was an aberration or a sign of things to come.

First Quarter Dropoff

Now I want to look at how Trubisky has performed in different quarters within a game, because there’s one that sticks out. All statistics here were compiled using Pro Football Reference’s Game Play Finder.

Trubisky has been markedly better in the first quarter than the others. In the first quarter, he’s performed like a superstar, while every other quarter has him looking like an average quarterback.

This is not a trend that was skewed by the Tampa Bay game either. In the first 3 weeks, Trubisky had a 113.2 passer rating in the first quarter and a 66.0 rating cumulatively in quarters 2-4. A 113.2 rating across a whole season would make him one of the best QBs in the NFL, while a 66.0 rating would be the worst starting QB in the league.

So why is Trubisky shining in the first quarter but struggling in quarters 2-4? We can’t know for sure, but my hypothesis is that it has to do with familiarity in the offense. The first quarter is when teams run largely scripted plays, which is to say the plays they worked on the most that week in practice. These are the plays that Trubisky will know the best, and they show just how dangerous he can be once he gets comfortable in the offense and knows the entire thing that well.

Of course, quarters 2-4 show just how raw he is and how much work is needed to reach that level. We saw way too much of Trubisky looking flustered and unsure of himself, unable to handle a blitz or move past his primary read in the first three weeks.

Again, was the Tampa Bay game an aberration or a sign of things to come? There Trubisky started hot like he always does, posting a passer rating of 147 in the first quarter. But instead of falling apart once they got past the scripted plays, Trubisky actually got better, posting a passer rating of 155 in quarters 2-4.

He’s not going to get a 150 passer rating every game, but if Trubisky can continue extending his first quarter play throughout the rest of the game, he will be a very good NFL quarterback.

Playing Style

Thanks to Next Gen Stats, we have some new metrics that let us evaluate how a quarterback is playing. All stats and ranks are through four weeks. These are not necessarily measures of the quality of his play, but more looking at his playing style.

For instance, Trubisky is averaging 2.53 seconds from snap to throw, which is the 5th fastest out of 37 quarterbacks ranked. This doesn’t mean he’s been the fifth best quarterback (Blaine Gabbert leads the league in fastest throwing), just that Trubisky has been mostly getting the ball out quickly.

Another metric where Trubisky ranks towards the top is in completion percentage; he has completed 2.4% more of his passes than their algorithm predicts based on the distance he’s throwing the ball. This ranks 9th of the 37 QBs.

In most other metrics he’s been somewhere near the middle of the pack. I’m just going to list them here for simplicity.

Average completed pass is 5.3 yards past the line of scrimmage, which ranks 15th.

Average attempted pass is 8.0 yards past the line of scrimmage, which ranks 20th.

The difference is 2.7 yards, which ranks 11th.

Trubisky is attempting 18.5% of his passes into tight coverage, which ranks 11th.

His average pass attempt is 0.7 yards short of the 1st down, which ranks 14th.

These aren’t necessarily stats saying he’s been good or bad, just interesting snapshots of his playing style. He’s getting the ball out quickly and completing lots of passes, and is around average in how deep he’s throwing the ball and how aggressive he is throwing into tight coverage.

Random tidbit: one area where we can say for sure Trubisky has been good is playing outside of the pocket. According to ESPN, he has a 113.8 passer rating in these situations, which is 5th in the NFL.

Where He’s Throwing

Finally I want to look at where Trubisky is throwing his passes. NFL Game Statistics and Information System provides us data about how frequently and how successfully Trubisky has thrown to different areas of the field.

Here’s the data for 2018 so far. The number of plays, completion percentage, and yards per attempt are given for six zones. Each zone is colored according to the average of the yards per attempt and completion percentage (green = top 10, red = bottom 10, yellow = middle 12); all ranks are through week 4.

A few thoughts:

Trubisky has avoided the deep middle of the field so far, but did not do so last year. I’m interested to see if that changes going forward.

He’s been bad throwing short middle, good throwing short right, and average to above average most other places.

There’s been a lot of talk about Trubisky throwing more frequently and more effectively to the right than the left, and generally that’s true here. He hasn’t been bad to the left, per se, he’s just been better to the right.

Looking at the NFL ranks for attempts, it appears he’s generally attempting more deep balls than short passes, at least relative to his peers. To be honest, this surprised me a bit, but the Bears do have the 6th most pass attempts that are 20+ yards past the line of scrimmage.

According to Next Gen Stats, Trubisky has thrown 2 TDs to his right, 3 to his left, and 3 to the middle. His three interceptions have been evenly split between the three sides. Pretty good balance there.

Lessons Learned

If you’re not one to sift through a bunch of data, here are my main takeaways from the numbers above:

The Tampa Bay game was great, but we don’t yet know if that was a fluke or a signal that better things are ahead.

Trubisky consistently plays well in the first quarter and is inconsistent outside of that.

Trubisky gets the ball out fast and completes a lot of passes, and otherwise has been a pretty typical QB in terms of playing style.

Trubisky has been great outside of the pocket.

Trubisky throws a bit more often and more effectively to the right, but his TD and INT are spread pretty evenly around the field.