LH = W? That's the equation for White Sox

South Siders' historic success vs. southpaws continuing in 2021

May 15th, 2021

After splitting a doubleheader with the Royals on Friday, the White Sox have MLB’s best record (23-14), winning seven of their past eight and 17 of 23. With the Twins unable to find their footing and the Royals crashing after a hot start, only Cleveland is challenging Chicago in the American League Central race.

Here’s another piece of good news for the White Sox: They are scheduled to face a left-handed starting pitcher on Saturday, when they host Kansas City and veteran Mike Minor.

In 2020, Chicago refused to lose against lefty starters, one reason the club made its first postseason appearance since 2008. But what seemed to be, in part, the quirky result of a short season is showing no sign of abating in 2021 -- at least, not yet.

The White Sox are 8-1 in games against lefty starters this season and 22-1 since last Opening Day. How rare is that? Some context, courtesy of the Elias Sports Bureau:

• Chicago’s .957 winning percentage against lefty starters since 2020 would be easily the highest for a team over any two-season span in the Modern Era (since 1900). The 1943-44 Reds (22-4, .846) are next on the list, while the 1941-42 Reds and 1942-43 Reds are the only other combos at .800 or higher.

• What about more recently? The second-best two-season record in the Divisional Era (since 1969) belongs to the 1969-70 Reds (56-20, .737), although the 2019-20 A’s (46-17, .730) were close.

• The only other team since 1900 to go 22-1 in any 23-game span against lefty starters was the 2004-05 Braves. Those Braves also are the only ones to put together a longer winning streak (18) against southpaws than Chicago’s 17, which ended April 11.

Coincidentally, Minor was the pitcher who had a hand in ending that streak, although he had to throw 85 pitches over four innings to do it, before six righty relievers finished a 10-inning victory. But the White Sox beat Minor (five innings, five runs) in a rematch last Sunday and then crushed Minnesota’s J.A. Happ (3 1/3 innings, nine runs) on Wednesday.

That brought the collective line for lefty starters against the club over the past two seasons to this: 23 starts, 0-17 record, 86 innings, 124 hits, 105 runs, 98 earned runs (10.26 ERA), 44 walks, 81 strikeouts. Only one time in that span did a lefty starter last at least five innings and allow fewer than four runs against Chicago (the Royals’ Kris Bubic last Aug. 30).

So before the Sox get their third shot at Minor on Saturday night at Guaranteed Rate Field, let’s take a deeper look at the club’s southpaw success.

How are they doing it?
It’s no surprise that the No. 1 ingredient required to win games started by a lefty is to hit the snot out of pitches thrown by lefties. The White Sox did that in 2020, when they slashed .285/.364/.523 in all plate appearances against southpaws and led MLB with a park-adjusted 142 wRC+. (That’s 42% better than the MLB average). And in 2021? They entered Friday hitting .317/.393/.512, with an MLB-best 157 wRC+ (higher than the overall career mark of any active hitter aside from Mike Trout).

Look beneath the surface, and it’s easy to see why. Entering Friday, and going back to 2020, the White Sox were tied for MLB’s seventh-lowest whiff rate against lefties (24.9%), while leading the Majors with a 10.8% barrel rate. If your quantity and quality of contact are both high, good things are going to happen.

We can put those factors together by looking at expected weighted on-base average (xwOBA), which takes into account exit velocity and launch angle, as well as strikeouts and walks.

Highest team xwOBA vs. LHP, since 2020
(Entering Friday)
1) White Sox: .358
2) Yankees: .348
3) Giants: .345
4-T) Dodgers: .344
4-T) Cardinals: .344

Granted, the White Sox also have benefited from the second-largest gap (23 points) between their xwOBA and their actual wOBA (.381), suggesting that some good fortune could also be at play. But there’s no doubt Chicago has been pounding left-handers.

Who is behind it?
As MLB.com’s Matt Kelly pointed out last September, no team in 2020 had right-handed batters take a greater share of its plate appearances (72.3%) than Chicago -- a key ingredient in making life difficult for lefty pitchers. But one interesting thing about the team’s continued success is that it’s down to 61.5% in 2021, which ranked a mere 13th entering Friday.

Why the change? Of five key right-handed batters on last year’s team, two departed in the offseason (Edwin Encarnación, James McCann), two haven’t played yet this season due to injury (Eloy Jiménez, Adam Engel), and another is currently injured (Luis Robert). (Fortunately, it seems that José Abreu won’t miss significant time after a collision Friday afternoon).

On the other hand, two other righties have emerged. MLB Pipeline No. 12 prospect Andrew Vaughn stepped into Jiménez’s spot, while 28-year-old rookie Yermín Mercedes came out of nowhere to take MLB by storm. That pair was batting a combined .422/.519/.756 in 54 plate appearances against lefties through Thursday, leading Chicago’s charge.

Is this for real?
If you are looking for reasons to be skeptical that Chicago will continue being unbeatable against lefties, you could simply point to the relatively small sample and believe the club’s performance in those situations will regress over time. (After all, the Sox have the fourth-fewest plate appearances against lefties since 2020, perhaps in part due to their prowess). It’s also worth noting a couple of other things.

  1. The team’s damage against lefties is really coming against lefty starters specifically. Entering Friday, the White Sox were far and away the No. 1 team in MLB in terms of wOBA against lefty starters since 2020 (.433). But they were essentially average against lefty relievers (.318, 13th in MLB).
  1. Between the regional schedule in 2020 and the early-season schedule in 2021, the Sox haven’t faced the most intimidating slate of lefty starters. (Frankly, there aren’t a ton of elite southpaw starters right now; of the top 25 starters in FanGraphs WAR since 2020, the only lefties are Clayton Kershaw and Hyun Jin Ryu). Still, of the 13 lefty starters (minimum 50 innings) with the lowest OPS allowed since 2020, only Happ and Rich Hill have tested Chicago’s mettle.

Still, consider this: Setting aside James Paxton, who sustained a season-ending injury 1 1/3 innings into his 2021 debut against the White Sox, Chicago has faced seven lefty starters this season and tagged them for an unsightly 14.02 ERA (40 earned runs in 25 2/3 innings). That includes crooked numbers against Happ (nine earned runs), the Royals’ Daniel Lynch (eight) and the Angels’ Andrew Heaney (seven).

Yet those seven pitchers entered Friday having thrown 195 innings this season against teams other than the White Sox. Their ERA in those appearances? Just 3.37.

So no, Chicago probably won’t maintain that pace. It almost certainly will lose some more games against lefties this year. But the Sox do look awfully dangerous in those matchups, and it’s helping fuel their 2021 success.