The Quest To Gain Platoon Advantage Takes A Left Turn, Part II

See also: The Quest To Gain Platoon Advantage Takes A Left Turn

In the first installment of the Platoon Advantage story, we examined the rising profile of the lefthanded reliever as well as the increasing dominance of lefthanded pitchers versus lefthanded batters, which is out of whack with the major league average as well as the other left/right platoon splits.

In this installment, we’ll go behind the numbers to try to determine what has led to the increasingly lopsided results favoring lefty pitchers in the same-sided matchup.

It’s The Pitchers, Right?

If one assumes that the quality of lefthanded hitters has not atrophied in the past decade, then one might conclude that something regarding lefthanded pitchers (or how they’re used) has changed fundamentally since 2001. At that point in time, the difference between a left-on-left matchup and a right-on-right one was negligible in terms of batting average, isolated power or strikeout rate (see previous installment for more). That’s no longer the case.

Lefthanders today are throwing harder than they once did, yes, but so too are righthanders, and the latter’s performance versus same-side batters has tracked closely with the major league average. That’s not the case for lefties, who continue to record more dominating results when they have the platoon advantage. Why is this?

Two facts cannot be disputed. Teams are relying more on lefthanders today than they have at any point since the mid-1990s, and also those lefties are facing lefthanded batters at an unprecedented rate. With a record 113 lefthanded pure relievers appearing in the big leagues in 2013, that’s not exactly a surprise, but it’s not relievers who are having all the fun. Baseball saw 41 lefthanded starters throw at least 100 innings in 2010, and that’s the largest number of regular southpaw starters in any one season during the Expansion Era (for pitchers making at least 75 percent of appearances as starters). The 2013 season ranked No. 2 with 39 regular lefty starters.

Rolling Three-Year Averages
Year PA vs LHP PA ft LoL
2002 24.5% 6.8%
2003 25.4% 7.1%
2004 26.5% 7.4%
2005 27.1% 7.5%
2006 27.1% 7.2%
2007 27.1% 7.2%
2008 27.6% 7.5%
2009 27.7% 7.9%
2010 27.9% 8.0%
2011 27.4% 8.0%
2012 28.2% 8.3%
2013 28.5% 8.6%

As to the point of greater left-on-left specialization, at right are the three-year rolling averages, beginning in 2002, for the percent of total major league plate appearances against lefthanders (PA vs LHP) and the percent of total PAs featuring a lefty pitcher against a lefty batter (PA ft LoL). All data from

The use of lefthanded pitchers marches on at a nearly uninterrupted pace, reaching maximum deployment this century during the past three seasons, when southpaws faced 28.5 percent of all batters. The single-season high-water mark in that time was 29.8 percent in 2012, which was the highest rate since 1992, when lefties faced 30.8 percent of all batters.

That’s nothing compared with the frequency of left-on-left matchups, which have not been more prevalent in the past 50-plus years. A full 9.2 percent of all plate appearances in 2012 featured a lefthander pitching to a lefthanded batter, and last year that figure dropped slightly to 8.7 percent. Those are the two highest rates of the post-1960 Expansion Era (and probably of all time).

It’s not entirely a case of relief appearances by lefthanders driving the matchup percentage, either. According to data shared with Baseball America by, relievers accounted for 47.5 percent of the total batters faced by lefthanders in 2013, a rate that is on the rise since 2010 but is not out of line with what baseball saw in 2003 (47.7 percent) or 1993 (47.4 percent). In fact, the highest rate for batters faced by lefty relievers happened in 1999 (52.4 percent) and has ebbed and flowed since then.

The difference now, of course, is that all relievers condense their effort into shorter stints than they once did, which enhances their overall effectiveness. (In 2013, for example, relievers posted a 2.78 SO/BB ratio, their best showing ever.) Instead of averaging six-plus batters per outing in the 1980s, or five-plus batters per outing in the '90s, relievers today average 4.4 batters per game. This undoubtedly has a positive effect on overall performance by relievers of all types, but given what we know about historical performance trends, this is particularly true for lefty relievers facing lefty batters.

“I think teams are putting more of a focus on left-on-left matchups and that’s changing the landscape of pitchers being used at the major league level,” a member of one National League front office said. “In the past, a pitcher would get called up because he has good stuff or good overall performance, and he’d remain in the league if he had success. That holds true today, but the definition of success has changed.”

Top Left-On-Left Relievers by OPS
2011-13 • min. 200 LH BF
Reliever l-OPS r-OPS Diff
Aroldis Chapman .363 .562 -199
Sean Marshall .456 .631 -175
Javier Lopez .467 .825 -358
Randy Choate .470 .765 -295
Jeremy Affeldt .524 .720 -196
Scott Downs .533 .707 -174
J.P. Howell .537 .756 -219
Glen Perkins .538 .654 -116
Rex Brothers .549 .736 -187
Marc Rzepczynski .554 .784 -230
Source: Baseball-Reference Play Index

Success for a reliever in the past might have been measured by basic metrics such as ERA or WHIP, or maybe overall utility as expressed by an even platoon split. Those measures, along with strikeout and walk rate, still are crucial for set-up relievers and closers, who work an inning or more at a time, but in today’s seven-man bullpens, managers have room for pitchers who fill niche roles.

“Specifically, for left-on-left relievers, we’re concerned with what they’re doing versus lefthanded hitters,” the front office member said. “In the past, the guy at Triple-A with the huge K-rate versus lefties but who struggled versus righties and, accordingly, had the high ERA might not get noticed the way he would today. So the pool of lefthanded pitchers today is more precise and focused on those who have had success versus lefthanded hitters.”

He also said that teams today are encouraging lefthanded relievers to find ways to improve their performance against lefthanded batters, even if those methods decrease their effectiveness against righties. Such steps might include lowering the arm angle, adopting a crossfire delivery that closes off the front shoulder and imparts more movement on the ball or throwing a sweeping breaking ball that’s difficult for the batter to track as it cuts across the plate to the outer half.

“Teams value the matchup ability, so they’re teaching pitchers to drop down and get a better angle on lefthanded hitters,” he said. “I can’t say this didn’t happen before—it likely did—but I think it’s happening more today.”

Look no further than the Rule 5 draft for examples of teams finding a rich vein for lefthanded relievers who give tough looks to same-side batters at the exclusion of any utility versus righthanders. Some of the most successful selections in recent years (in relative terms) have been lefthanded relievers.

The Diamondbacks took Joe Paterson third overall in the 2010 draft and kept him around for the entire 2011 season, including the playoffs. The Mariners used the third pick in 2011 to select Lucas Luetge, and he made 63 appearances for Seattle in 2012. Cesar Cabral, a Dominican lefty who signed as an international free agent with the Red Sox in 2005, has been so popular in the Rule 5 that not only has he been drafted twice (2010 and 2011), but he passed through three organizations via various transactions before landing with the Yankees in 2012. Despite spending the better part of 2012 and 2013 on the disabled list with an elbow injury, Cabral remains on New York’s 40-man roster. He made 30 rehab appearances last year, but nevertheless has faced just 15 big league batters in two years, where, naturally, lefties are 1-for-8 with six strikeouts against him.

Two of the more practical selections in last year’s Rule 5 draft project to be low-slot lefty relievers Patrick Schuster (Padres) and Brian Moran (Angels). Coming off disappointing 2013 seasons, San Diego and Los Angeles identified lefthanded relief as an area to address for 2014, the former having dealt Joe Thatcher at the trade deadline and the latter having lost Sean Burnett to an elbow injury. All it costs to speculate on Schuster and Moran is $50,000 and a 25-man roster spot, right?

Or Might It Be The Batters?

Not everybody in the industry is convinced that lefty pitchers have established a new level of dominance so much as lefty batters either have not evolved their approach at the same rate or are not subjected to the same standards as are righty batters.

“I’m not sure we can assume that, as a group, the quality of lefthanded hitters hasn’t atrophied in the past decade,” said one member of an American League front office, “at least insofar as their performance against lefthanded pitchers is concerned. I have no idea if this is true, but I could see it being possible that the swings and approaches of a greater number of lefthanded hitters aren’t conducive to hitting same-side pitchers.”

Clayton Kershaw

Clayton Kershaw threw a slider or curve nearly 37 percent of the time last year. (Photo by Bill Mitchell)

This theory makes anecdotal sense. Many lefthanded batters prefer the ball down and in so that they can drop the bat head on the ball and loft it for power. The fact that so many lefthanded pitchers work away from this hot zone versus lefty batters—typically favoring the slider, cutter or curveball as a No. 2 or 3 pitch—speaks to the method’s level of acceptance. (It’s also why righthanded starters need a good changeup to dominate quality big league lineups featuring lefty balance.) But as to the lefthanders, Clayton Kershaw threw a slider or curve nearly 37 percent of the time last year, according to pitch-type data presented at; Cliff Lee threw a cutter or curve 28 percent of the time; Chris Sale threw a slider nearly 30 percent of the time; David Price threw a cutter or curve 29 percent of the time; Jon Lester threw a cutter or curve 35 percent of the time, and so on.

“Of course, you’d also expect righthanded hitters to struggle equally versus righthanded pitchers, but that doesn’t show in the data as much,” the AL executive said. “Since there are so many more righthanded hitters—and they have to be fairly proficient at dealing with same-side breaking balls to even get to the big leagues—it may be that this characteristic isn’t being selected out as lefthanded hitters ascend to the big leagues in the same way it is for righthanders.”

In other words, due to the preponderance of righthanded pitchers in the majors—they accounted for roughly 70 percent of games started in 2013—a young, righthanded hitter must demonstrate proficiency against same-side pitchers to ascend to the status of big league regular. If he doesn’t, he might have to wait several years to get a shot at the short end of a platoon role. The same is not true for lefthanded hitters because of the industry’s bias in their favor. This is especially true at first base and in the outfield, where a larger percentage of players bat lefthanded, because those are the only field positions where those who throw lefthanded can play.

The AL front office executive posited another theory. “It’s possible that the increase in left-on-left at-bats isn’t just an indication of greater usage of lefthanded pitchers,” he said, “but also an unwillingness, or an inability, on the part of managers to platoon or pinch-hit for their lefthanded hitters.

“If that’s the case—and they’re less protected against same-side pitchers than righthanded hitters are—you might expect to see the decline in production. Perhaps increasing specialization in the bullpen has led to a dearth of roster flexibility in other areas, including short-side platoon bats.”

Now we’re back to where we started. Managers today strive to achieve the platoon advantage for their pitcher/defense via late-game maneuvering as much as possible, when the opposite was true 20-plus years ago.

If the theory that lefty batters are less “protected” than they used to be is true, then we should expect to see a larger percentage of plate appearances being taken by lefthanded-hitting regulars versus lefthanded pitchers than we once did. The graph below maps that trend from 1998, baseball’s last expansion year, to present, with a “regular” defined as any player taking at least 350 PAs in the season examined. Coming to bat 350 times would account for roughly three and a half months of everyday play—a clear majority of the season—plus it’s also half of the 700 PAs teams consume annually at many lineup spots. (Note that the y-axis begins at 20 percent, not zero. Split data derived from Baseball-Reference Play Index.)


Pct of LHP faced by LHH Reg


If you accept the operational definition of a “regular” above, then it’s true that lefthanded-hitting regulars are, in the big picture, facing more lefthanders than ever before, possibly because they’re not as frequently being “protected” by a platoon or by pinch-hitters. Lefty-hitting regulars faced southpaws 29.6 percent of the time in 2012, the highest percentage of the last 16 seasons. We saw some correction last year with the figure falling to a a more typical 27.1 percent, but overall the three-year moving average is at virtually its highest point since 1998.

What’s Next?

Thirteen of the 32 Cy Young Awards handed out since 1998 have gone to lefthanders: Tom Glavine (1998), Randy Johnson (1999-2002), Barry Zito (2002), Johan Santana (2004, 2006), C.C. Sabathia (2007), Cliff Lee (2008), Clayton Kershaw (2011, 2013) and David Price (2012). However, the overall strikeout rate for lefty starters compared to the league average rate for starters has shown no overall trend in that time, bouncing up one year and down the next.

The area where regular lefty starters (min. 100 innings) have shown clear progress is in the department of strikeout-to-walk ratio, which because of a plummeting walk rate has improved steadily from 1.98 in 2003 to 2.84 in 2013. Given the recent work from the likes of young southpaws Madison Bumgarner, Gio Gonzalez, Kershaw, Matt Moore, Price, Jose Quintana, Chris Sale, et al., maybe the notion of lefties developing later than righties no longer applies. (At the same time, the crop of lefthanded prospects is historically weak in 2014—at least until North Carolina State’s Carlos Rodon turns pro—with the Marlins’ Andrew Heaney checking in at No. 30 on the Top 100 Prospects. The previous worst showing for the top southpaw: 1997, when another Marlin, Felix Heredia, checked in at No. 43.)

Given the improved dominance and control for all lefthanded pitchers, baseball may be in store for another course correction, this time with teams limiting exposure by lefthanded batters to lefthanded pitchers. We’ve seen teams such as the Athletics, Indians and Rays have success with a broader strategy of platooning in recent years, and as with everything else in baseball, it takes only one success story to give rise to mimics.