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Estimating a pitcher's Ws

TDs3nOut

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I have had a fantasy team in an espn roto league for each of the past four years. After never finishing above fourth place before last year, I finally won my league last year. I am looking forward to this year’s draft and a chance to “defend my title” (LOL). To that end, I am trying to devise a strategy for identifying starting pitchers that are strong in the following four statistical categories: Ws, Ks, ERA, and WHIP.

The other day I mentioned to a poster on another forum that chasing the W stat for pitchers in a roto league has often led to bad decisions that end up hurting both my WHIP and ERA. That poster, who is a very experienced roto fantasy player posted that he tries to get SPs who have low WHIPs and high Ks/9, since he finds that by doing that Ws tend to take care of themselves. He also feels that such pitchers, in addition to getting Ws, tend to have low ERAs.

Accordingly, in order to investigate this proposed strategy, I constructed a data set for all MLB pitchers who last year made ten or more starts. I then used these data to estimate two regression models. In the first I model Ws as a linear function of both WHIP and Ks/9. While WHIP is highly significant in this model, Ks/9 is not. Likewise, in the second model, where ERA is estimated as a linear function of WHIP and Ks/9, I again find that WHIP is highly significant but Ks/9 is not.

Since Ks/9 was not a reliable predator of either Ws or ERA, I began thinking about how it seems to me that guys who get a lot of strikeouts also often throw a lot of pitches and aren’t able to stay in the game long enough to earn a W. Accordingly, I modified each of the two models above by substituting Ks for Ks/9.

In the first of these two new models, where Ws are modeled as a linear function of both WHIP and Ks, both WHIP and Ks are highly significant. In the second, where ERA is modeled as a linear function of these two variables, however, while WHIP is again highly significant, Ks is not.
So, of the four models that I estimated, here is the only one in which both independent variables are statistically significant:

A pitcher’s estimated wins = 6.69-3.56(his WHIP)+.06(his Ks)

A couple of pitchers whose performances fit this model almost perfectly last season are Mike Minor and Hiroki Kuroda. The two pitchers last year who most underperformed (in the sense that they won far fewer games than their WHIP and Ks predicted) are Cole Hammels and Tyson Ross. And the two pitchers who most outperformed the model (in the sense that they won far more games than their WHIP and Ks predicted) are Bartolo Colon and Jorge De La Rosa.

Finally, if anyone has made it this far in this post, feel free to post your thoughts on either this approach or alternative approaches to identifying starting pitchers in a roto league who can help your team in the Ws, Ks, ERA, and WHIP categories, without doing so at the expense of any of the others of these categories.
 

TKOSpikes

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Very interesting. I would say there is definitely something to that math, however, I'm sure there are many "exceptions" to the rule and sorting them out would be incredibly difficult. If it was laid out in front of me as a graph or chart, I'm sure it would be a very useful tool come draft day.

I would totally agree though, and it's already my most used "statistical decision", with the WHIP. Sure I like to know if he can strike guys out, but if it's a Jonathan Sanchez style where you're lucky to get the 5th inning out of him, it's gonna hurt his chances for W's, WHIP and everything important. Therefore, you can't go all-in on the K guys.

You would also want to take a look at potential for an innings bump (for younger starters).
 

MilkSpiller22

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yea, i dont think strike outs is any relevance to a win/loss... I would say the 3 stats that predict wins the best(pitcher individual stats) are:

1. ERA- obviously, the less runs a pitcher lets up the more likely he can leave the game with the lead

2. WHIP- low whip might suggest that the pitcher does not let up many unearned runs

3. Innings- the longer you go into a game the more likely you will come out with a decision...

I dont see strike outs doing much good in predicting!!!
 

MilkSpiller22

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but you could really just do QS%*innings pitched/(9* games started)

I am sure that that would be a great predictor...
 

TDs3nOut

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Very interesting. I would say there is definitely something to that math, however, I'm sure there are many "exceptions" to the rule and sorting them out would be incredibly difficult. If it was laid out in front of me as a graph or chart, I'm sure it would be a very useful tool come draft day.

I would totally agree though, and it's already my most used "statistical decision", with the WHIP. Sure I like to know if he can strike guys out, but if it's a Jonathan Sanchez style where you're lucky to get the 5th inning out of him, it's gonna hurt his chances for W's, WHIP and everything important. Therefore, you can't go all-in on the K guys.

You would also want to take a look at potential for an innings bump (for younger starters).

You are right about both. There are 185 pitchers in the data that I used. The absolute value of the average difference between each of these pitcher's actual wins and estimated wins is about 2.8, so the model is far from perfect.

Your comment about "sorting out" the exceptions to the rule reminds me that there are obviously other variables besides WHIP and Ks that are potentially useful in determining how many Ws a pitcher will get. One that I frequently pay attention to when I choose pitchers is how many runs does his team typically score, which might be another good variable to include in the model.
 

TKOSpikes

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One that I frequently pay attention to when I choose pitchers is how many runs does his team typically score, which might be another good variable to include in the model.

Be careful doing that though, as I believe that is where the term "chasing wins" comes from, and that can be fatal in fantasy.
 

TDs3nOut

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yea, i dont think strike outs is any relevance to a win/loss... I would say the 3 stats that predict wins the best(pitcher individual stats) are:

1. ERA- obviously, the less runs a pitcher lets up the more likely he can leave the game with the lead

2. WHIP- low whip might suggest that the pitcher does not let up many unearned runs

3. Innings- the longer you go into a game the more likely you will come out with a decision...

I dont see strike outs doing much good in predicting!!!

Well, it turns out that Ks are pretty highly correlated with Ws. Without getting technical, one way to see this is to think about guys like Sherzer, Kershaw, and Wainwright, who had both high K and W totals last year. At the other extreme, you have guys like Capuano and Danks who have both low K and W totals. Overall, Ks is statistically significant.
 

TDs3nOut

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Be careful doing that though, as I believe that is where the term "chasing wins" comes from, and that can be fatal in fantasy.

LOL True enough, and something I know all too well! That's why ideally I would want a guy who plays on a team that scores a lot of runs and who also has low WHIP and high K totals. Problem is, of course, there aren't a lot of those guys and they tend to be on another owner's roster!
 

MilkSpiller22

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Well, it turns out that Ks are pretty highly correlated with Ws. Without getting technical, one way to see this is to think about guys like Sherzer, Kershaw, and Wainwright, who had both high K and W totals last year. At the other extreme, you have guys like Capuano and Danks who have both low K and W totals. Overall, Ks is statistically significant.


their wins though were because ERA... Bartolo colon had 18 wins, why?? because of his ERA, he does not strike people out... high strike out rate to the players with wins really just shows that generally speaking pitchers who strike out batters are the better pitchers... But of course you need ERA first...

Just saying that it is much less important than innings,ERA and WHIP... just like in any other judgement of a pitcher...
 

MilkSpiller22

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But again i see the best predictor(using only individual pitcher stats) is QS%*Innings/(9*Games started)

and you can easily see why...
 

MilkSpiller22

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But again i see the best predictor(using only individual pitcher stats) is QS%*Innings/(9*Games started)

and you can easily see why...


More accurately since we are just predicting wins and not percentage the best predictor is:

QS%*innings/9

Dont think you can come up with a better predictor without taking into account the run support a pitcher gets...
 

tlance

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I have had a fantasy team in an espn roto league for each of the past four years. After never finishing above fourth place before last year, I finally won my league last year. I am looking forward to this year’s draft and a chance to “defend my title” (LOL). To that end, I am trying to devise a strategy for identifying starting pitchers that are strong in the following four statistical categories: Ws, Ks, ERA, and WHIP.

The other day I mentioned to a poster on another forum that chasing the W stat for pitchers in a roto league has often led to bad decisions that end up hurting both my WHIP and ERA. That poster, who is a very experienced roto fantasy player posted that he tries to get SPs who have low WHIPs and high Ks/9, since he finds that by doing that Ws tend to take care of themselves. He also feels that such pitchers, in addition to getting Ws, tend to have low ERAs.

Accordingly, in order to investigate this proposed strategy, I constructed a data set for all MLB pitchers who last year made ten or more starts. I then used these data to estimate two regression models. In the first I model Ws as a linear function of both WHIP and Ks/9. While WHIP is highly significant in this model, Ks/9 is not. Likewise, in the second model, where ERA is estimated as a linear function of WHIP and Ks/9, I again find that WHIP is highly significant but Ks/9 is not.

Since Ks/9 was not a reliable predator of either Ws or ERA, I began thinking about how it seems to me that guys who get a lot of strikeouts also often throw a lot of pitches and aren’t able to stay in the game long enough to earn a W. Accordingly, I modified each of the two models above by substituting Ks for Ks/9.

In the first of these two new models, where Ws are modeled as a linear function of both WHIP and Ks, both WHIP and Ks are highly significant. In the second, where ERA is modeled as a linear function of these two variables, however, while WHIP is again highly significant, Ks is not.
So, of the four models that I estimated, here is the only one in which both independent variables are statistically significant:

A pitcher’s estimated wins = 6.69-3.56(his WHIP)+.06(his Ks)

A couple of pitchers whose performances fit this model almost perfectly last season are Mike Minor and Hiroki Kuroda. The two pitchers last year who most underperformed (in the sense that they won far fewer games than their WHIP and Ks predicted) are Cole Hammels and Tyson Ross. And the two pitchers who most outperformed the model (in the sense that they won far more games than their WHIP and Ks predicted) are Bartolo Colon and Jorge De La Rosa.

Finally, if anyone has made it this far in this post, feel free to post your thoughts on either this approach or alternative approaches to identifying starting pitchers in a roto league who can help your team in the Ws, Ks, ERA, and WHIP categories, without doing so at the expense of any of the others of these categories.

There are plenty of guys who get a lot of Ks, but are an absolute ratio killer because they walk too many. I am referring to guys like Tim Lincecum. You do not want that.

What you want are pitchers with BOTH a high K/9 and a low WHIP. Not 1 or the other. By focusing on those two stats together, you can weed out some pitchers who get consistently overvalued and also find a few diamonds in the rough.

Innings eaters who get few Ks can play well in points leagues, but they don't play well at all in many roto style leagues unless you are free to stream or you have weekly line-up deadlines.
 

tlance

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Bottom line though, statistical models based solely on a pitcher's numbers cannot predict wins. Clayton Kershaw should have won 22 games last year based on how well he pitched, but the W stat is largely outside of the pitchers control.

You can guestimate run support based on how good the pitchers supporting offense will be, but again I think this is an exercise in futility. Numbers can't predict Cliff Lee's inability to win in 2012. If you are too hung up on that particular stat, you will miss the boat because the other 3 are much easier to project.
 
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Brees#1

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One strategy I learned last year was using Jesse Crain and Rosenthal who allowed little runs and pitched in 7th/8th innings. Their low ERA and WHIP would help against overall ERA and WHIP as well. This did help as I was very strong in this category once I played this strategy out in addition to trying not to start pitchers in likely bad matchups. With the setup pitcher strategy there is more room for error in the event a 8 run game happens to a pitcher.
 
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