I’ve got to shorten these up or I’m never going to finish them. So here goes this:

The Major League second basemen in April: Luis Castillo, Alex Cora

Overview: Luis Castillo is my favorite player in the Major Leagues. I just decided that this morning, on my train ride into work, when I was thinking about writing this preview and thinking about Luis Castillo.

At one point, Castillo was a good defender. That’s no longer the case. At one point, he stole lots of bases. He doesn’t do that a ton anymore, either.

But Luis Castillo perseveres, because Luis Castillo is really really good at what he does. And what Luis Castillo does is get on base without any discernible batting power, no small feat.

Check it out: In this decade, a player has posted an isolated slugging (slugging average – batting average) of less than .100 with an on-base percentage over .350 in over 500 plate appearances 48 times.

That seems like a lot, I realize, but over 10 years, that means it only happens 4.8 times a season. And Castillo is responsible for eight of the 48 instances. No other player has done it more than four times.

For fun, keep the other qualifiers the same and knock the ISO down to .060, and it’s only happened 12 times in the aughts. No one but Castillo has done it more than once, and Castillo has done it five times.

Poke around the Fangraphs.com plate discipline leaders for the past few years. Every season he qualifies, Castillo swings at fewer pitches outside of the zone than nearly every other batter in the Majors, and makes contact with more of the pitches he swings at than nearly anyone else.

This, I’m certain, is all tied up with the lack of power, and it’s not something you need any fancy stats to identify. Dude has quick wrists and a good eye, and usually chops or slaps at the ball.

Because of his abject refusal to swing at bad pitches and his tendency to put good ones in play, Castillo has maintained a good on-base percentage even as the rest of his skills have eroded. And because the ability to get on-base is the most important offensive skill, Castillo is still a worthwhile Major League hitter, no matter how frustrating it is to know he’ll almost never put one past an outfielder, especially from the left side of the plate.

Castillo is a weird outlier among Major League hitters, and I love weird outliers in general. That’s why he’s my new favorite player.

That shouldn’t be misconstrued to mean I think he’s good, though. His near-hilarious lack of range in the field will hurt the Mets this year, as will his big contract the team is unwilling to see as sunk cost. But those are just two more parts of the Castillo mystique.

It’s a safe bet that as long as Castillo is “healthy” — a relative term, in his case — and on the Mets, they’ll be trotting him out to second base, where he’ll take a couple of steps and fall and flail in the general direction of ground balls hit his way. And at the plate, he’ll keep doing his thing, slapping at balls thrown over the plate, taking balls that are inches off of it.

The Major League second basemen in September: Castillo, Cora

There’s certainly a non-zero chance Castillo gets hurt and Ruben Tejada gets a look, but while I really like Tejada and think he’s an underrated prospect, he’s quite young and will probably be given plenty of time to develop as long as Castillo’s healthy. Plus, there’s that whole contract thing.

Reese Havens is a solid bet to be a quick-mover, too. But he’ll be playing his first full season at second base. Shouldn’t be a terrible transition from shortstop, but he’ll have to work on turning the double-play from that spot, hurdling over oncoming runners and Luis Castillo’s big contract.

How they stack up: Chase Utley is better than Luis Castillo in every conceivable way. Martin Prado probably is too. Dan Uggla might be the only second baseman in the Majors who’s worse than Castillo, but it’s pretty close, and he’s a better hitter. Adam Kennedy is a better defender and had a nice year at the plate for Oakland in 2009, but I’m not guessing that will continue.

So even with his impressive on-base percentage, it’s hard to call Castillo anything more than the second-worst second baseman in the division. And if the OBP slips, the defense gets worse or Kennedy maintains his 2009 offensive output, Castillo will be the worst.