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What’s going on with Jon Lester?

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... and can he turn it around?

Photo by Stacy Revere/Getty Images

Jon Lester has had a rough August. In five starts this month he’s gone 1-3 and racked up the following line: 24⅓ IP, 37 H, 25 R, 23 ER, 12 BB, 24 K. I’ve spent the better part of this week trying to figure out what’s behind this sustained downward stretch. I took a look at a variety of elements, including velocity, pitch selection and catchers to try and figure out if this was just a random downward turn he’d come out of or if something is structurally wrong.

The stats

Since August 1 opposing batters are absolutely crushing the ball against Lester. They are slashing .346/.408/.523 against the Cubs lefty. The good news is that to some extent Lester has been the victim of bad luck. He’s currently got an 8.51 ERA for August, however, his FIP over the same time period is 4.85 and his xFIP is 4.76. Don’t get me wrong, neither of those is good by any stretch of the imagination, but they also aren’t over 8. Currently a lot of the damage hitters are doing against the Cubs lefty is being bolstered by an unsustainable .407 BABIP.

That said a FIP near 5 isn’t exactly great either, so I wanted to take a look at what may be contributing to Lester’s slump. For reference, here are Lester’s stats by month:

Lester stats by month

Month IP BB/9 K/9 HR/9 ERA FIP xFIP
Month IP BB/9 K/9 HR/9 ERA FIP xFIP
Mar/Apr 19.0 2.84 9.00 1.42 2.37 4.21 3.73
May 33.2 1.87 8.29 1.07 4.28 3.63 4.74
June 35.1 1.78 10.19 2.04 4.33 4.74 3.71
July 26.0 2.08 6.92 1.04 2.77 3.86 4.36
August 24.1 4.44 8.88 1.48 8.51 4.85 4.76
Select stats Fangraphs

You can see pretty clearly that walks have contributed to a lot of Lester’s problems in August. While he’s getting about the same number of strikeouts compared to the rest of the season, he’s also putting a lot of runners on base. Additionally, he’s not getting out of situations where there are runners on. His LOB percentage for August was 55.3 percent compared with 75.5 percent from March through July.

New catchers

One of the variables I wanted to take a look at was who was catching Lester, and not just because Willson Contreras is my favorite. Lester is known for having strong preferences for catchers (it’s the primary reason David Ross was a Cub). Prior to his extended time on the Injured List beginning at the start of August, Willson had caught every Jon Lester start in 2019.

Now that said, Lester’s problems started with Willson behind the plate. On August 1 he was touched up for nine hits and five runs, all of them earned, over five innings against the Cardinals. It was not one of his best games. You can see the pitch location for that game below:

Pitch map August 1
Baseball Savant

You’ll notice that there are a large number of pitches up, Lester tends to be better when he’s painting the low corners as we’ll see in a second.

When Willson hit the IL, Victor Caratini caught Lester’s next two starts against the Athletics and the Reds. The Reds start was not great. The Athletics start was an unmitigated disaster. You can see both of those pitch maps below:

Pitch map August 6
Baseball Savant

The pitch location here is also up, although the horizontal range is a bit narrower. Lester was hit hard in this game. His final line was: 4 IP 10H 11R 9ER 3BB 6K.

Pitch map August 11
Baseball Savant

Lester’s second game with Caratini behind the plate went much better. His location wasn’t great, but he’s staying down in the zone more. This resulted in 5 IP, 5 H, 3 R, 3 ER, 3 BB, 7 K.

Jonathan Lucroy took over catching duties for Lester starting with the Little League Classic and both the results and the pitch map were better:

Pitch map August 17
Baseball Savant

He’s staying down more and there is a lot more clustering in the corners. This was by far Lester’s best start of the month, but he still walked way too many guys. He went 6IP 4H 0R 0ER 5BB 3K.

Lucroy also caught Lester’s last start against the Nationals. I think you all know this one didn’t go well: 4⅓ IP, 9 H, 6 R, 6 ER, 1 BB, 2 K:

Pitch map August 23
Baseball Savant

Pitch selection and velocity

From the above maps I noted two things, the first is that Lester has had some control problems, he’s not hitting the locations he’d like to consistently and as a result he’s walking too many guys. It does look like his brief experiences with Lucroy were better than his experiences with Caratini. However, I also wanted to make sure nothing strange had happened in terms of his velocity or pitch selection.

First up, velocity. Good news, Cubs fans: Lester’s velocity is the same as it ever was, at least in 2019. This doesn’t appear to be related to arm fatigue:

Lester’s velocity by pitch by month - 2019
Brooks Baseball

However, when I started to look at pitch selection there was a real aha moment. Lester’s pitch makeup has been a bit all over the place in 2019. To demonstrate this, the next graph includes both 2018 and 2019 and shows the percentage of pitches Lester has thrown by type each month:

Pitch usage by month 2018-19
Brooks baseball

In particular Lester’s fastball and cutter have traded off more through 2019. To a smaller degree, he’s done the same with his curve and change up. Interestingly, while his pitch usage does appear to be a reaction to batters hitting certain pitches harder than others, his month by month attempt to adapt to that does seem new. Here is the same time frame for SLG against by pitch:

SLG against Lester by pitch type by month 2018-19
Brooks Baseball

Notice that there is a similar variance in SLG against in 2018 with a lot less pitch selection variance.


Lester has always struck me as a creature of habit and August has thrown him a lot of curve balls. In addition to getting used to two new catchers, he’s manipulated his pitch selection more this season than in previous years. He’s still at his best when he can paint the low outside corner with his cutter. I’d look for Lucroy to continue to catch him until Contreras is back, and if he can get back to controlling his cutter better he should rebound nicely in September.