How well do hot streaks predict the future performance of pitchers?

Over the past couple weeks, I’ve looked at how predictive hot and cold streaks are for hitters. Given that a hitter is on a hot or cold streak, how likely is it that the streak will continue in the next game? While I found nothing to indicate hot streaks have much predictive value, I did find that there might be something to cold streaks. Over the next two weeks, I’ll be doing a similar study for pitchers. Today, I’m going to examine their hot streaks.

The Study

I’ll be using a very similar methodology I used for hitters. To study hot streaks, I’ll be comparing the stats from the pitcher’s 3-start streak to his next start. I’ll then compare the pitcher’s preseason Marcels projection to his next start. This will tell us which is more predictive – a full projection for a player or the streak. When comparing these sets of numbers, I’ll be using average error to study the differences.

I looked at all possible 3-start streaks for all pitchers back to 1993 that occurred in either March, April or May (I did this so that the preseason projections would be as accurate as possible – if we’re looking at streaks in August, it’s likely the player’s projection would have changed considerably by that point in the season). From there, I only included a streak if all three starts came within an 18-day window and the fourth start came no more than a week after the third. No context adjustments were made to the data.

“Hot” Pitchers – 3 starts

While I’ll be looking at a number of different stats, I decided to define a “hot” streak based upon FanDuel points accumulated (based on FanDuel’s MLB 35k format). The average pitcher accumulates roughly nine points per game, so to be included among the “hot streak” population, a pitcher must have averaged at least 15 FanDuel points over a three-start period. Here are the average errors for a number of different stats, keeping in mind that the lower the number is, the better. All stats were scaled to league average before comparison (except FanDuel points, for clarity’s sake).

As we saw with hitters, for all stats that we look at, the preseason projection is a far better predictor of the start immediately after a 3-start hot streak than the hot streak itself is.

“Hot” Pitchers – 5 starts

If we repeat the study over a five-start period (starts must have come within a 30-day window), we get the following results:

Same thing. Hot streaks don’t appear to hold much water even after 5 starts.

“Hot” Pitchers – 7 starts

Repeating the study for seven-start periods (starts must have come within a 42-day window), our results look like this:

Nope. Even once a pitcher has been hot for over a month, we’re still better off using a very basic preseason projection than using the streak. It gets close for a few stats, but after 7 hot starts, we’re looking at close to a quarter of a season’s worth of starts for a pitcher, so his in-season projection would likely have changed considerably by then and the gap would increase (remember, the projections we’re using for our comparison test are from before the season).

Final results

Just like we found with hitters, no matter how long a hot streak lasts or what stat we look at, it appears that using a projection (even a preseason projection as simple as Marcel) is far superior than trusting that the streak will continue.

Concluding thoughts

That wraps it up for this week. Next week, I’ll wrap up this series on streaks with an examination of cold streaks for pitchers. Also, you’ve probably noticed that my article has been appearing on seemingly random days of late, but going forward, you’ll be able to find my article here at FanDuel every Tuesday morning.

As always, if you have any questions, feel free to comment or e-mail me. Also, be sure to add me as a friend on Facebook and follow me on Twitter.

Derek Carty’s work can also be found at Baseball Prospectus, CardRunners Fantasy Baseball, and DerekCarty.com. He has previously had his work published by The Hardball Times, NBC’s Rotoworld, Sports Illustrated, FOX Sports, and USA Today. He is the youngest champion in the history of LABR, the longest-running experts league in existence, and is a graduate of the MLB Scouting Bureau’s Scout Development Program (aka Scout School). He welcomes questions via e-mail, Facebook, or Twitter.

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