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Updating Verlander’s Chance at 25 Wins

Posted By __Jack Moore__ On September 8, 2011 @ 2:11 pm In __Daily Graphings__ | __49 Comments__

At the end of August, amid the beginnings of Justin Verlander‘s entry into MVP discussions, I investigated his chances at winning 25 games this season, a feat that hasn’t been accomplished since Bob Welch did it for the 1990 Athletics. Using two methods, I came to the conclusion that Verlander had anywhere from a 5.7% chance to a 29% chance of winning 25 games (although our best estimates likely come on the lower end of the spectrum), assuming he would start five games between August 29th and the end of the season (which looks like it’ll be the reality). Now, Verlander is a 22-game winner, earning victories in his past two starts despite allowing four earned runs in Wednesday’s victory over Cleveland.

A reminder of the first estimate, the absolute upper bound on his chances:

For our first estimate, let’s use something relatively simple. So far, Verlander has 22-5 win-loss record in 31 starts. Verlander has a “start win percentage” of .709, as he’s won 22 of his 31 starts this year.

Using this extremely simple method, Verlander would have a remarkable 36% chance at winning 25 games this year, up from 29% two starts ago.

Now, for the more meaningful method:

The method is based on the Marcel projections featured here — so simple a monkey could do it, as long as he had a working understanding of the SQL programming language.

For a Marcel-type projection, we weight the past three years on a 5-4-3 basis (most recent gets 5, then 4, then 3), and add in two seasons (68 starts) of an average pitcher. Remember, we’re concerned with start winning percentage here, not decision winning percentage. Of the 1,854 games started in the American League this year, 678 of them have been wins. That’s a start winning percentage of only .366 for the American League. That number goes with a .690 start win percentage this year in 29 starts, .545 in 2010 in 33 starts, and .543 in 2011 in 35 starts.

Using this method, we get a winning percentage of .570, slightly up from our .564 from earlier. Using this number, we arrive at an 18% chance of winning 25 games.

Given the fact that this year’s Tigers squad is a bit better than the teams he’s played for lately, we can probably elevate that number a bit. What we really want here is a range of probabilities, and given this data, I would feel pretty comfortable assigning a probability of 15%-25% for Verlander’s probabilities of winning 25 games.

Even in this brave new world of very few exciting postseason races, at least we’ll have something to watch for as Verlander approaches a milestone untouched since 1990.

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