The Complexity and Simplicity of David Ortiz vs. Mike Napoli

The good news for the Red Sox: they’re in the World Series! That’s amazing! And they have home-field advantage, too, thanks to the heroes and zeroes included in this box score. At this point, while both the Red Sox and Cardinals are quite good, you have to think of the Red Sox as being the favorites. Yet, there’s bad news for them as well: as an American League team with a quality designated hitter, they’ll have a decision to make before the games in the National League ballpark. David Ortiz and Mike Napoli can both hit the crap out of the ball, but when Boston’s in St. Louis, one of them is going to have to sit, at least for the first several innings.

John Farrell has already gone on record as saying that Ortiz will start at first base at least once, maybe twice. And, who knows, he’s free to change his mind at any point, since he’s the one who draws up the lineups. It’s only natural to want to investigate the same question. Who should start at first in St. Louis, between Ortiz and Napoli? Which starter would most increase Boston’s win probability, and thus Boston’s World Series win probability? Getting to the answer is almost impossibly complex. Because of that, in a way, it’s also unthinkably simple.

The framework for this analysis is simple. You compare the players’ abilities at the plate. You compare the players’ abilities in the field. Whoever comes away looking better ought to start. And, to begin, some very important points: Ortiz bats left-handed, Napoli bats right-handed, and the Cardinals are expected to start Joe Kelly, Lance Lynn, and Adam Wainwright in Games 3-through-5. All three of those pitchers are righties, meaning Ortiz would have the platoon advantage.

We can look at 2013 platoon numbers, but you should never really look at single-season platoon numbers. Going back five years, Ortiz has been about 50 points of wOBA better than Napoli at the plate against righties. Going back three years, the difference is 35 points. Let’s call it 40. Over four plate appearances, that’s a difference of about 0.13 runs. Over five plate appearances, that’s a difference of about 0.17 runs. That’s a pretty substantial gap, as you’d expect, since Ortiz is an offensive beast, and he’d have the advantage on his side.

As for defense? Well, for the first time, this season Napoli was a full-time first baseman. For his career, UZR calls him about five runs above average per season, but a lot of writers are convinced that Napoli took defensive steps forward in 2013, which would make sense given that he was able to shed all catching responsibilities. Maybe he’s actually a +10. With Ortiz, it gets tricky, because he hardly ever plays defense anymore. His career numbers as a first baseman call him a -5, but almost all of his innings came more than a decade ago, and now he’s almost 38. Is he more like a true-talent -10? Perhaps even -15 or -20? The worst defensive first baseman of the UZR era is Mo Vaughn, who shows up at -16.5 per 150 games. Then we have a handful of guys between -12 and -13. Those are players who were allowed to play first, and Ortiz pretty much hasn’t been. The defensive gap between Napoli and Ortiz is pretty enormous, as these things go.

If you think the defensive difference between Napoli and Ortiz is ten runs or so over a year, then Ortiz is the obvious start in St. Louis. If you think the gap is more like 20-25 runs, then it’s pretty much all balanced out. And this can get so much more complicated still. Ortiz is a considerably worse baserunner than Napoli, dinging him a few more fractions of a run. You never think of baserunning as being a reason to make a decision like this, but everything is a factor, and Ortiz is one of the worse runners around, which you could assume just by observing his body and his regular position.

What about the opposing pitchers specifically, though? Kelly is early in his career, but so far he has a pretty pronounced platoon split, which isn’t surprising given his sinking fastball. Lynn has allowed a .350 wOBA to lefties and a .278 wOBA to righties over a greater sample. Over a very big sample, Wainwright has a pretty ordinary platoon split. So, no reverse platoon splits to worry about here — Ortiz would certainly have the advantage as a left-handed bat. Yet you could drill down into specific pitch types if you wanted, and that could present a better idea yet.

What’s the state of Ortiz’s body these days? What about Napoli’s? Are they both more or less 100%? Are they feeling a little worn down from the long season? How has Ortiz looked in practice fielding grounders and throws? Is there any reason to believe Ortiz would perform differently as a hitter if he’s asked to field instead of sit and wait? Would you expect him to hit better or worse? What about leveraging pinch-hit appearances — would you rather have Ortiz or Napoli available late off the bench? Are you willing to replace Ortiz with Napoli late, even though Trevor Rosenthal and a lot of the Cardinal bullpen is right-handed? Do you pitch differently with Ortiz at first than with Napoli at first, trying to allow fewer balls in play in the first-base area?

That’s a paragraph full of questions, none of them completely unreasonable. John Farrell is going to have a very difficult decision to make, two or three games in a row. But here’s the thing about difficult decisions: decisions like this are difficult because there isn’t necessarily an obvious answer. And if there isn’t an obvious answer, that means the projected outcomes are similar, which means the decisions themselves are of only minor significance. If it’s really hard to tell the overall difference between starting Ortiz and starting Napoli, that means the decision would have little effect on win probability, which would make it a surprisingly easy decision. If you can’t tell, then at the end of the day, it doesn’t really matter.

Myself, I suspect Ortiz is the better start, as many as three games in a row if the series isn’t a sweep. I think he has a big enough offensive edge, especially if there’s anything to the respective platoon differences in 2013. However, there’s a substantial defensive gap between the two players, and that gap erodes a lot of Ortiz’s offensive edge. Maybe it even erodes all of it — I don’t know. I don’t know how the Sox feel about Napoli’s defense vs. Ortiz’s defense. If they’re going to start Ortiz in St. Louis, it stands to reason they don’t think the defensive gap wipes out the offensive gap.

But it’s close. The end result of the calculations is that it’s close, and when a decision is close, it’s more and more difficult to identify a right and wrong answer. Mostly because the right is less right, and the wrong is less wrong. Picking between David Ortiz and Mike Napoli feels like a super important decision, and things could certainly play out that way, with one of them being a series hero. But this is one I’m happy to leave to managerial discretion, and based on the numbers, the decision shouldn’t be as important as it seems. The important thing is that the Red Sox have to pick in the first place. How they pick? It doesn’t shift the chances much.

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Jeff made Lookout Landing a thing, but he does not still write there about the Mariners. He does write here, sometimes about the Mariners, but usually not.

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