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Jon Lester’s Lefty/Righty Splits This Year Are a Lot Bigger Than You May Have Realized

Analysis and Commentary

Describing Jon Lester’s 2017 season using a single word, like good or bad, isn’t too easy.


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On the one hand, his 4.30 ERA and 4.05 FIP are WELL above his career averages and he may fail to be worth 3.0 fWAR for the first time since 2012.

On the other hand, that ERA and FIP are both better-than-average in the current run scoring environment, he’s been disproportionately hurt by a few really bad starts, and he’s already started 29 games this season (165.1 IP), which means he should make a full slate of 32 by the end of the year.

But there’s an angle to consider on the lack of overall dominance that we haven’t discussed this year.

As I was writing the Series Preview for the Cubs/Rays two-gamer yesterday morning, I was rifling through Lester’s stats and noticed something rather striking: his lefty/righty splits for this season.

Versus Lefties: .206/.233/.343, 35.1% K rate, 2.7% BB rate, 13.25 K/BB, .245 wOBA; 2.19 FIP
Versus Righties: .268/.341/.459, 21.3% K rate, 9.3% BB rate, 2.27 K/BB, .340 wOBA; 4.65 FIP


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Now, it’s not particularly crazy to see a southpaw deal against fellow lefties while letting righties hit him better, but those numbers against righties are scary, and Lester’s lefty/righty splits are far more pronounced this season than ever before.

Look at the graphical difference in wOBA and FIP between lefties and righties for Lester over the years. Negative values show seasons where righties have hit him better (regular splits) and positive values show seasons where lefties have hit him better (reverse splits):

In three years (2009, 2010, and 2014), Lester has been tougher against righties than lefties. In 2008, 2011, 2012, 2013, and 2015-2017, then, Lester has had normal splits. Most of the time, the splits have been small, in any case.


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But can you see the obvious spike this season? Never have righties handled Lester as well as they have this year, and the only year close is his first full professional season back in 2008.

The same is true for the difference in his FIP:

No matter which way you slice it, it seems 2017 is an outlier, in terms of Lester’s lefty/righty splits.

Now check out his fWAR totals by season:

*2008: 4.1 fWAR
*2009: 5.3 fWAR- Reverse Split Year
*2010: 4.8 fWAR- Reverse Split Year
*2011: 2.7 fWAR
2012: 2.5 fWAR
*2013: 3.5 fWAR
*2014: 5.6 fWAR- Reverse Split Year
*2015: 5.0 fWAR
*2016: 4.4 fWAR
2017: 2.5 fWAR

The years in which Lester’s splits are reversed (2009, 2010, and 2014) represent three of the best four seasons (by fWAR) of his career – with only the 5.0 fWAR he posted in 2015 interrupting the trend (and that was his first season in the National League, when hitters were less familiar with him).


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So clearly (if not, obviously), Lester is better when righties aren’t taking extra advantage of him. So perhaps we should try to find out why righties are hurting Lester more here in 2017 than ever before.

Looking at his pitch mix in 2017 compared to those three more-successful-against-right-handers seasons (2010, 2011, and 2014), I can say nothing really stands out. The combination varies slightly over time, but for the most part, he’s using his four-seamer, cutter, sinker, change-up, and curveball as much (or nearly as much) as he did during those three seasons.

(Photo by Justin K. Aller/Getty Images)

With that said, he’s throwing his four-seamer WAY less this season (38.3%), than he has in the last four years (44.4% average). And that’s probably because, for the first time since 2012, his four-seamer has been a negative value pitch. And unfortunately, that’s probably not wholly unrelated to the fact that his fastball velocity has never been lower.

In 2017, Jon Lester’s four-seamer, according to FanGraphs, has averaged just 91.7 MPH. In the nine seasons from 2008-2016, on the other hand, he’s average 93.4 MPH. It’s not unusual for pitchers around Lester’s age to start losing/continue losing velocity, but that doesn’t change the fact that it can hurt his production.


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From where I’m sitting now, it seems like Lester had ramped up his fastball usage in recent years to some success, but had to cut back on it this season as his velocity dropped off considerably. Perhaps that lost 1.5 MPH or so, then, was all right-handers needed to pounce and throw off his lefty/righty mix.

Although righties are doing relative damage against all five of Lester’s pitches this year, we have to keep in mind that all pitches are related, especially where a guy like Lester is trying to “tunnel” them to look the same, and play each pitch off of each other. A loss of velocity/effectiveness in one pitch could, in turn, make his other pitches less effective. In support of that theory: righties are swinging and missing far less often this year against Lester’s changeup and curveball (Brooks), which could be related to their ability to sit back a little bit longer before triggering their swing.

It’s worth pointing out that Lester’s cutter has also declined by about 1.5 MPH in velocity this year, and has seen a commensurate jump in slugging by righties (from .308 last year to .428 this year). The big issue there has been a sharp decline in groundballs he’s getting from righties against his cutter: from 45.76% last year to just 34.95% this year.

With all of this said, I want to point out that although righties have even made better contact against Lester this season than lefties, he’s still a solidly above average contact manager against all types of hitters.


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And on top of that, he’s rocking a .309 BABIP, a 68.1% strand rate, and a 16.3% HR/FB ratio, all of which are much worse than his career marks. So, it’s not unfair to say that there’s probably some bad luck cooked into this, as well.

In the end, I can’t yet definitively say why righties are hitting Lester so much better this year than before, but it certainly seems that fastball velocity (and, thus, four-seam value) is playing a big role. I wonder, then, if he’ll continue to scale back the four-seamers against righties and attack them in different ways.

Plenty of pitchers reinvent themselves after losing velocity, and someone with a wide repertoire like Jon Lester has the best chance of succeeding. As we’ve seen this year, he’s still capable of spinning good starts, and perhaps with a year like this one to adjust, he’ll come back improved in 2018.

Brett Taylor contributed to this post.


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Michael Cerami

Michael Cerami is a Writer at Bleacher Nation, and you can find him on Twitter at @Michael_Cerami.