Sinister Split: The Mets Against Left-Handed Starting Pitchers

The season is about 50% over and the Mets seem like 70% of a strong contender. This estimate is based on two key facts:

1. About 70% of innings across the league are thrown by right-handed pitchers.
2. About 70% of the Mets' innings have been thrown by their starters.

Yes, the bullpen has floundered, posting an ERA just under 5.00 and a strikeout-to-walk ratio just over 2.00, and the team has struggled to win games started by lefties (they currently have a 12-20 record against left-handed starters), but they have overcome those apparent weaknesses to make some real noise in the National League.

With contention comes scrutiny, though, and a lot of people have been dissecting the Mets' roster lately, with good reason. If their strengths can hold up — you have to expect some regression from the starters, who have been excellent — and they can improve the bullpen, the Mets could be a scary team.

On the surface, a right-handed platoon bat seems like a great investment for the Mets. Their lineup is extremely left-handed — they have taken 57% of their plate appearances from the left side, the fourth-most in the league — and their .375 winning percentage against left-handed starters (compared to .624 vs. righties) seems to speak for itself. Scott Hairston has been a revelation against left-handers and one more bat like his, in place of Josh Thole, Kirk Nieuwenhuis, Lucas Duda, or Ike Davis seems like it could help them close that gap.

Dig a little deeper, however, and you’ll find something surprising. Despite the fact that the Mets' OPS is about 70 points lower against lefties than righties, they have scored more runs and hit for a higher OPS in games started by left-handed opponents.

How is it possible that a team which struggles against lefties has scored more when the opposing starter is a lefty? A number of factors come to mind.

1. The platoon split is larger for relievers than it is for starters.
2. The Mets can control who faces the starter, adding more righties to the lineup when facing a lefty starter.
3. The Mets have performed better against the bullpen in these starts, perhaps due to seeing inferior members of the bullpen.
4. Starting more right-handed bats against left-handed starters can help to neutralize left-handed relief pitching.

Whatever the reason, it should be clear that the Mets' sub-par record against left-handed starters this season has hinged more on their pitching than their batting. They have allowed almost twice as many runs in games in which they were facing a left-handed starter. Part of this can be attributed to defense, by trying to get more righties into the lineup they often take a hit defensively, but let’s be honest: defense is never the Mets' strong point. There must be a considerable amount of luck involved here.

Would the Mets benefit from adding an additional right-handed bat? Yes. The Mets have faced lefties in 36.7% of their plate appearances — the highest percentage in baseball — in part because they feature so many lefties in their lineup. Percentage of lefties faced correlates strongly with percentage of team plate appearances by left-handed batters, likely because opposing managers are more likely to use left-handed relievers against lineups stacked with lefties. However, it’s important to understand exactly what position your team is in and where exactly they need help. I’d expect the Mets' winning percentage platoon against lefties to regress heavily in the second half, even if they don’t change anything. Knowing this may alter the type of right-handed bat which the Mets will try to acquire.

Just this morning it was reported that the Mets might be interested in acquiring Ramon Hernandez from the Rockies, though I’m not sure that a right-handed catcher is the best player for the Mets to target. While Hernandez would be an upgrade over Mike Nickeas, it would be more difficult to use him off the bench because managers are reluctant to use their backup catcher as a pinch-hitter, so Hernandez would mainly have an impact in those games started by left-handed pitchers. Even in those games, his value would be attenuated somewhat as one-fifth of Mets games are started by R.A. Dickey, and it's unlikely that anyone besides Thole would be asked to catch those games regardless of the handedness of the opposing starter.

A right-handed corner outfielder, one who would allow the team to sit either Davis or Lucas Duda — and play the other one at 1B — against lefties, would be more effective at lowering the impact of left-handed relievers on the team, which appears to be their true weakness. The Mets may not even have to go outside the organization to address this, since Jason Bay should be back from the disabled list soon. Notwithstanding Bay, another right-handed bench bat who could be deployed in pinch-hitting situations against lefty relievers may be where the Mets should set their sights.