If all goes according to plan, the top four spots of the 2013 White Sox' rotation will be balanced between left-handed and right-handed pitchers. Assuming health, right-handers Jake Peavy and Gavin Floyd are a lock. Lefty ace Chris Sale has a spot secured, of course, and if he returns healthy from shoulder surgery, so does lefty John Danks. So go the top four: We've got a pair of pitchers for each arm.
After that, though, it gets weird. The candidates for the fifth spot, Jose Quintana, Hector Santiago, Charlie Leesman, are all left-handed. Assuming an even distribution, if the top five pitchers each stayed healthy, lefties would start 97 games for the Sox this season, or 60 percent of their total games. A team rarely gets through a season having used only five starting pitchers, though, and Peavy and Floyd have both missed significant time to injuries. If the White Sox need a spot start or 10, it's likely to come from that same group of left-handers. As such, there's a pretty good chance that upward of 100 White Sox games -- maybe significantly upward -- will be started by a left-handed pitcher.
That seems like a lot. In 2012, less than 30 percent of all batters faced in the major leagues went to left-handed pitchers, and only about 32 percent of all games were started by lefties. The White Sox are looking at twice the normal frequency of lefty pitchers as a starting point, and possibly significantly more than that. This intuitively seems like a bit of a problem. Since most hitters are right-handed, the White Sox will be going in on the wrong end of the platoon advantage for most of their opponents' plate appearances in the first five-to-seven innings of most games.
On the other hand, though, the left-handed pitcher's' lefty-on-lefty advantage is bigger than the righty-on-righty one; in 2012, righties put up a .704 OPS vs. fellow righties, lefties only .648 against lefties (against opposite-handed pitchers, lefty batters outperformed righty ones by six points). All else being equal (which it never is), you'd usually rather have a left-handed pitcher out there than a right-handed one; having "too many" lefty starting pitchers only works if you figure your opponents are free to stack their lineups with right-handed hitters, which probably doesn't really work when your opponents are limited to 25-man rosters and have something like 17 other teams to match up against in a given season.
Overall, then, it probably doesn't make much sense to say a team has "too many" left-handed starting pitchers. Perhaps balance matters in that it might make some difference, but that has to be a much smaller factor than the overall quality of the pitchers themselves; it makes far more sense to go with the best starters you can find, and figure the balance will work itself out, than to worry about their handedness.
Nevertheless, let's go further. Have similarly lefty-heavy starting rotations tended to come up against any particular problems?
Since 1950, there have been 22 teams who gave at least 100 starts to left-handed pitchers. Here are the eight (the latest coming in 1983) who have had at least 110 lefty starts -- that's at least 68 percent of their 162-game season -- and a little something about each:
1965 Los Angeles Dodgers: We're starting with a bang. These Dodgers won the World Series, and are often thought of as one of the all-time great pitching teams, though a lot of it was the park and era they got to pitch in. Don Drysdale started 42 games -- 25.9 percent. Of the remaining 120 games, 112 of them -- 93.3 percent -- were started by left-handed pitchers, led by Sandy Koufax (41 starts), Claude Osteen (40) and Johnny Podres (22). The Dodgers' lefty-heavy ways clearly didn't hurt them in the standings. They held lefties and righties to an almost identical OPS (.625 right, .626 left), which masks a bit of left-handed superiority, since lefty hitters league-wide were 27 points better than righties. Still, the Dodgers were dominant against all comers, which suggests, if nothing else, that Koufax and Drysdale starting more than half your team's games is a good thing.
1974 Baltimore Orioles: Jim Palmer had fronted the Orioles' rotation for most of the preceding five seasons, but an elbow injury in 1974 limited him to 26 starts. That meant three lefties -- Ross Grismely, Mike Cuellar and Dave McNally -- combined for 114 starts; throw in two spot starts by Don Hood and 71.6 percent of the team's games were started by southpaws. It went almost as well for the Orioles as it had for the Dodgers; they won 91 games and the AL East, only to lose the ALCS to the Athletics. The per-batter effect was similar to that of the Dodgers: a .670/.665 righty/lefty OPS split, neutralizing lefties' .679/.718 advantage league-wide.
1975 Chicago White Sox: The second most lefty-heavy rotation since 1950, the ‘75 Sox gave the bulk of their starts to three workhorses: Jim Kaat (41 starts and 303 ⅔ innings), Wilbur Wood (43 and 291 ⅓), and Claude Osteen (37 and somehow only 204 ⅓). They weren't good workhorses, save Kitty, but they sure took the ball every three or four days. In all, 124 of the team's 161 starts (77 percent) went to southpaws. The results weren't good, but that's because the pitchers weren't. Kaat's 126 ERA+ and Goose Gossage's 212 (in 141 ⅔ relief innings) buoyed the team ERA and kept it right around average; nearly everything else was a flaming pile. Moreover, the staff actually did better overall against righties than lefties, holding the former to a .709 OPS while permitting a .778 against the latter. Much of that was likely Gossage's .418/.721 righty/lefty split.
1979 Chicago White Sox: The South Side loves its lefties! This team, which left us Disco Demolition Night to remember it by, gave 116 of its 160 starts (72.5 percent) to left-handers. It was a totally different group from the ‘75 squad: Ken Kravec, Rich Wortham, Ross Baumgarten and Steve Trout. If those names don't ring a bell, it's probably for good reason, though save for Wartham they were decent that season. Lefty batters still hit better off the Sox than righties (.726 to .706), but the advantage was slightly less than among big-league hitters overall (.744 to .717).
1980 New York Yankees: Tommy John, Ron Guidry, Tom Underwood, and Rudy May combined for 109 games started for the Yankees, with Tim Lollar chipping in the 110th (67.9 percent). Luis Tiant and a handful of right-handed rentals and swingmen handled the remaining 52 games. The team won 103 games, though the lineup and bullpen were both bigger strengths than the starting rotation. Lefties actually hit much better against the Yankees than righties did that season, with a .776 OPS to .661, but Goose Gossage was on this team too and no doubt contributed to that, along with Ron Davis -- the two righty relievers combined for 230 innings, and Davis in particular decimated his fellow righties.
1980 Chicago White Sox: Yep, it's the White Sox again -- and while the makeup was largely unchanged from 1979, here Britt Burns got the most starts, followed by Trout, Baumgarten, Kravec, and Wortham, who (with one more start by a lefty reliever) combined to account for 111 of the team's 160 starts (69.4 percent). This team was worse than the previous year's squad, losing 90 games, though you couldn't blame Burns (143 ERA+ in 238 innings), Trout (110 in 199 ⅔), or Baumgarten (118 in 136), and actually, the staff as a whole was pretty decent; the team was sunk by a poor offense. Here again, left-handed batters did better than righties: .741 to .698, virtually identical to the big-league averages in both cases.
1982 Kansas City Royals: Lefties took 113 of Kansas City's 162 starts (69.8 percent). They were led by Larry Gura (37 starts and 248 innings), Vida Blue (31 and 181), Paul Splitorff (28 and 162) and Buddy Black (14 and 88 ⅓). The problem with these guys wasn't that they were too left-handed, but that for at least that season, they simply weren't good enough to support an excellent Dan Quisenberry-led bullpen and George Brett and Hal McRae-led lineup. The Royals won 90 games with that subpar rotation, but finished three games behind the Angels for the AL West crown. They were more or less equally effective against lefties (.735 OPS) and righties (.724)...but neither was terribly impressive.
1983 New York Yankees: This, an almost entirely different squad from the 1980 team, was the most lefty-heavy rotation since 1950 and the last one to top 110 starts by southpaws. Between sole 1980 holdover Guidry (31 and 250 ⅓), Shane Rawley (33 and 238 ⅓), Dave Righetti (31 and 217), Bob Shirley (17 and 108), and Ray Fontenot (15 and 97 ⅓), 127 games out of 162 (78.4 percent) were started by someone of the sinister persuasion. The Yankees won 91 games -- good only for third in the East -- and the rotation generally got the job done, with Shirley the lone weak spot among the lefties. The team had a .719/.650 righty/lefty split against, compared to the big-league average of .704/.729.
As we expected at the outset, history hasn't had much to tell us. Teams with a disproportionate number of left-handed starters may tend to struggle a bit, relatively speaking, against the majority of hitters who are left-handed, but they've got a very large advantage against the left-handed ones, and it all seems to more or less come out in the wash. Or, rather: there probably are some very real advantages and disadvantages to running a lefty-dominated rotation, but the impact of those differences is likely dwarfed by a number of other factors, including -- and most notably -- the actual skill of the pitchers involved.
Turning back to 2013, the White Sox may have a more significant advantage or disadvantage if the AL Central were particularly heavy or light on left-handed hitters, but that isn't the case: The Tigers, Twins, and Indians each have three left-handed hitters in their projected lineups, and the Royals four. It's worth noting that most of the Tigers' key hitter, the Sox' strongest likely rival, are right-handed or righty-leaning switch hitters; Austin Jackson, Torii Hunter, Miguel Cabrera and Victor Martinez all figure to benefit from Chicago's left-handedness, with only Prince Fielder to balance the scale, if you will.
Still, if there is one lesson here it's that skill mitigates handedness. There, at least if Peavy and Sale remain healthy and Danks can get healthy, the White Sox have a pretty significant advantage - this is a very, very talented rotation. It might be dominated by guys who write with their wrists awkwardly crooked and never learned how to use standard-issue scissors properly, but there is no reason to worry that that makes it any less than the very good rotation in appears to be.