Of the approximately 150 pitchers to begin this season in the starting rotation of a big league team — we say “approximately” because some teams have taken advantage of early off-days to avoid using a fifth starter — 45 are left-handed. That’s just below 30 percent of expected starts going to southpaws, which aligns nicely with the actual percentage of plate appearances that came against all lefty pitching last season (29.8 percent).
That’s a sizable amount of plate appearances to account for, and so clubs must construct their rosters with the ensuing platoon splits in mind. But not all lefty starting pitching is created equally, and here we’re talking about much more than just the obvious differences between Clayton Kershaw  and Jeff Francis . Whether by design or by circumstance, left-handed starting pitching is no way dispersed equally throughout the big leagues — some teams have to deal with up to four times as many southpaw starters in their divisions than others.
By mapping the lefty starters in each division against offensive tendencies, we can identify contenders who are most hurt and helped by the uneven distribution of southpaws.
Hurt: New York Yankees
On Opening Day in the Bronx, the Yankees faced lefty starter Jon Lester  and his Boston Red Sox. As one might expect, Yankee manager Joe Girardi  attempted to respond by loading his lineup with as many right-handed bats as he could against the Boston southpaw.
Last year, when the club had the fourth-best wRC+ in baseball against lefty pitching, that lineup would have included Derek Jeter , Russell Martin , Alex Rodriguez , Mark Teixeira , and Nick Swisher .
But this season, limited by various injuries and a tight offseason budget, the best Girardi was able to come up with was a group that included bench players and castoffs like Ben Francisco , Jayson Nix , Eduardo Nunez , and Vernon Wells . The quartet combined for just two walks in 12 plate appearances; the Yankees ended up falling to their rivals by a score of 8-2.
It’s fair to note that the litany of problems facing the Yankees this season stand to give them trouble against pitchers of all shapes and sizes, but the rag-tag lineup underscored a larger concern — the club looks to have an extremely serious problem hitting southpaws in 2013. Of the 10 Yankees on the current active roster who had at least 50 plate appearances against left-handed pitching in 2012, only Travis Hafner , Nunez and Kevin Youkilis  managed even a league-average wRC+ against southpaws. Hafner is unlikely to see much time against lefties, so that leaves New York with a large portion of their lineup that will struggle to hit southpaws — yes, even Robinson Cano , who had only a 78 wRC+ against his fellow lefties.
That’s a big problem in a division where every team except Baltimore has at least two lefty starters, including defending Cy Young  Award winner David Price  and up-and-coming star Matt Moore  in Tampa Bay. While the Red Sox added lefty-killers Mike Napoli  and Shane Victorino  this winter and the Toronto Blue Jays can still rely on Jose Bautista  and Edwin Encarnacion , the Yankees can best hope to tread water while hoping their injured right-handed stars return sooner than later.
Hurt: Los Angeles Dodgers
If you don’t like lefty pitching, then the NL West is a tough place to be. Each team here starts the season with two lefties in its rotation, which means that every club has to prepare to see eight lefty starters within the division — tied with the Baltimore Orioles, Miami Marlins, and New York Mets for the most in baseball.
The Dodgers may luck out in that they don’t have to face their own ace lefty (Clayton Kershaw ), but it’s a bigger problem for them than their rivals because the club has serious problems against lefties. They finished tied for 24th in wRC+ against southpaws in 2012, and the 2013 roster isn’t exactly built to improve upon that. The most notable addition to the lineup this year is Carl Crawford , who brings just an 83 wRC+ against lefties over his career, and the inability — or unwillingness — to find a suitable platoon partner for Andre Ethier  (76 wRC+) has plagued the team for years.
While a full season of Adrian Gonzalez  (career 115 wRC+ against lefties) rather than James Loney  (77 wRC+) at first base will ameliorate that somewhat, the loss of Hanley Ramirez  (135 wRC+) to injury for most of the next two months is going to further inhibit the club against southpaws. More than anything, the team needs Matt Kemp  to prove he’s fully recovered from offseason shoulder surgery to destroy lefty pitching as he did in 2011.
He’s been unable to do that in the early going, and if not, the team could be in for more than a few games like the one they suffered through on Tuesday, when Madison Bumgarner  dominated them over eight shutout innings.
Helped: Cincinnati Reds
There are only five lefty starters in the NL Central, and the Reds and Milwaukee Brewers are both actually going with all-righty groups after Aroldis Chapman  and Chris Narveson  ended up in the bullpen. What’s more, since three of those five are Jeff Locke , Jonathan Sanchez , and Travis Wood , it’s not exactly as though the lack of quantity is being made up for with high quality.
The lack of tough southpaw starters in the division benefits the Reds, who traded lefty-killer Drew Stubbs  over the winter and just lost Ryan Ludwick  (coming off a very good 149 wRC+ against lefties last season) for the next three months after dislocating his shoulder. That doesn’t mean they’ll be totally punchless against the lefties they do see, because Joey Votto  hits absolutely everyone and Todd Frazier  showed success against southpaws last year, but this is now a team that’s well-equipped to handle righty pitching.
That’s a tendency which is shown in the splits, because Votto (192 wRC+ in 2012 against righties, as opposed to 145 wRC+ against lefties), Jay Bruce  (128/99), Shin-Soo Choo  (160/78), Jack Hannahan  (100/78) and Brandon Phillips  (102/96) all hit better against righty pitching than lefties last season. That’s the heart of the Cincinnati order, and Chris Heisey , expected to fill the Ludwick void, has had better success over his career against righty pitching as well.
This is a good Reds team that should be able to hit no matter who is on the mound, but this can give them a slight edge in a division they were already favored by many to win.
Helped: Kansas City Royals
The only place with fewer lefty starters than the NL Central is the AL Central, which started the year with only two southpaw starters once Scott Kazmir  landed on the disabled list. While Chris Sale  is a quality pitcher, Jose Quintana  still has much to prove.
That’s good news for the Royals, who beat out only the Cleveland Indians and non-contenders Chicago Cubs, Houston Astros, and Marlins in wRC+ against lefties in 2012. Ned Yost ‘s club had 14 different hitters gather at least 50 plate appearances against southpaw pitching last season, and a mere three — Billy Butler , Lorenzo Cain , and Salvador Perez  — managed to be league-average.
That leaves an awfully large amount of plate appearances against southpaws that generally ended poorly, whether it was the 201 times up for Eric Hosmer  (a horrendous 63 wRC+), 179 to Jeff Francoeur  (79), and even 254 to Alex Gordon  (84). There’s some hope here because Perez is now healthy and expected to see more playing time, and Francoeur traditionally has been better against lefties, but the Royals made few changes on the offensive side of the ball, importing only Elliot Johnson  and his 67 wRC+ against lefties in 101 plate appearances.
For a team desperately trying to break a losing skid that’s measured in decades, every little advantage can help, and this works in Kansas City’s favor.