Luis Castillo goes for a 30-game hit streak today. In this AP article on ESPN.com, I found this quote interesting:

The Marlins' leadoff man and second baseman is strictly a singles hitter. His 52 hits during the streak included just four for extra bases. He had walked only four times, partly because pitchers don't want to give the leading base-stealer in the major leagues a free pass.

In other words, he's the kind of scrappy batter likely to put together a hitting streak.

I've had some fun with the probabilities of hit streaks over the years. One thing I've found is that batters who walk a lot are a lot less likely to have hit streaks than batters that don't. Why? Because the probability of a hit streak depends on something I call hit average which I define as Hits/PA (plate appearances). If you have two players with the same batting average, the one with fewer walks will have the higher hit average (but a lower OBA), and will in general be more likely to have a longer hit streak.

For example, take two .300 hitters. One draws 100 walks and gets 165 hits in 550 AB. The other draws 50 walks and gets 180 hits in 600 AB. Both have 650 PA. The first player has a hit average of .254, while the 2nd player has a hit average of .277. The first player, however, has an OBA of .408, while the 2nd player has an OBA of .354. So if you need to get someone on base, send up the first player. If you need a hit, send the 2nd. Right now, Castillo is more like player 2.

The other factor in determining the probability of a long streak is the number of times you come to the plate in a game. The more times you step up to the plate in a game, the more likely you are to get a hit in one of those PA. Let's take our player with the .277 hit average as an example:

                Prob. of at

PA in Game      least 1 Hit

         1          .277

         2          .477

         3          .622

         4          .727

         5          .802

So if you can get 5 PA in a game, you have an 80% chance of getting a hit. Batting leadoff, Castillo is maximizing his chances of getting the extra AB. So things are looking good for a long streak by Castillo. His hit average this year is .302. That gives him an 83% chance of getting a hit in a 5 PA game. He gets 5 PA in roughly 3 out of 5 games he plays. Given those numbers, I give Castillo a little better than 21 in 500 chance of hitting in another 28 straight games. Not outlandish odds. Maybe this will generate some fan interest in the Marlins.