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Stolen Bases and Diminishing Returns

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Stolen Bases and Diminishing Returns

Postby Pokey » Mon Feb 15, 2010 12:00 am

I'm sure this issue has been discussed on these forums before, but I couldn't find anything with a cursory search. The issue I'm referring to is that of valuing stolen bases when projecting and ranking your players. I like numbers. So when I do projections for roto, I like to assign a number value to those projections. I know that ranking players in a tier system is en vogue, and probably more useful, but, indulge me.

The quickest and easiest way to turn projections into ratings is to divide the players projected contribution in a particular category by your target number in that category. This is problematic with stolen bases, because a player like Ellsbury can provide you with almost half of your target for the category by himself, which throws his value way out of wack. Does anyone have a way to tweak a formula in order to account for the diminshing returns in value of stolen bases?
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Re: Stolen Bases and Diminishing Returns

Postby Y`s Guy » Mon Feb 15, 2010 1:26 am

You male Ellsbury seem like a one-dimensional guy when he will reward you in AVG and RUNS, too.
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Re: Stolen Bases and Diminishing Returns

Postby Pokey » Mon Feb 15, 2010 2:47 am

For sure. Not trying to take anything away from Ellsbury. But my point is, using the simple projections to ratings method I detailed above (and multiplying by 100 to get easier numbers to work with) If Ellsbury steals 70 bases again next year, that's going to be somewhere around 45 to 50% of your target number (hence Ellsbury is awarded 45-50 points), but no one is going to get you more than 12 or 13 points from any other category, so in this system, steals guys are way overvalued because it has no way to account for diminishing returns on the value of steals (ie, you need HR contributions to some extent from everyone on your team to be in the top-3 of your league whereas its possible to be top-3 in steals with just 3 or 4 guys contributing).

I'm just wondering if anyone has any strategies for correcting for this.
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Re: Stolen Bases and Diminishing Returns

Postby kab21 » Mon Feb 15, 2010 6:44 am

This is a problem with any mathematical equation for player valuation. the math is correct but if you just followed it then you would end up with 500 SB's. It doesn't matter if you used the equations from rototimes, J35J, yourself or myself (I've played around with this). the problem is SB's aren't valued the same in the draft as they are according to the math. This isn't terribly different in the MLB from how defense was very undervalued until recently or the moneyball focus on OBP (it was undervalued at the time). One reason for this is that there is far less certainty in SB numbers. That's just a guess but I feel safe speculating that an individual players SB's vary significantly more than his HR's.

Another thing that knocks down the values of the SB specialists is that some of them are marginal starters (based on offense). Take the Morgan, Pierre, Bourn and Rajai Davis types. these guys are .350ish OBP guys with .380 SLG. If these guys slump they are prone to moving to the bottom of the lineup and/or losing PT. that could be devastating for a fantasy team that might be depending on one of these guys for 30-50% of their SB's.

I've never worked on it enough to implement a solution. But you could just multiply SB's by a decimal value to reduce how much they are worth in your equation. Maybe something between 0.60-0.80. J35J uses his math as a quick and dirty sort and then adjusts the rankings based on his opinion. A pretty solid option imo.
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Re: Stolen Bases and Diminishing Returns

Postby MotorCityKitties » Mon Feb 15, 2010 11:09 am

This is something I've seen with Shandler's rotisserie rankings at the end of his forecaster book. Guys like Michael Bourn are ranked in the top 50 this year. In years past Juan Pierre was always ranked in the top 20. Perhaps you can just bump these guys down in your rankings, but keep in mind what they do for you in steals.
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Re: Stolen Bases and Diminishing Returns

Postby jake_twothousandfive » Mon Feb 15, 2010 12:38 pm

kab21 wrote:I've never worked on it enough to implement a solution. But you could just multiply SB's by a decimal value to reduce how much they are worth in your equation. Maybe something between 0.60-0.80. J35J uses his math as a quick and dirty sort and then adjusts the rankings based on his opinion. A pretty solid option imo.

This is exactly what I thought of as well. As you fill up your positions, simply adjust the weighting for each category accordingly.

Very simple, yet effective. The solution will have to be something easy like this so you can adjust it on the fly.
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Re: Stolen Bases and Diminishing Returns

Postby GotowarMissAgnes » Mon Feb 15, 2010 12:46 pm

There are several different things to consider.

1. nonlinearity in value: in most cases the guys who finish 1/2 in most categories are going to be significantly above the trailers. So, when you calculate something like standings gain points in roto, you have to recognize that it because nonlinear at the top and bottom of the scale.

2. Dynamic value: as you and your competitors make picks, the value of each player to each of you changes, depending on how the cat totals change.

So, you may want to adjust your valuations to account for that. For example, you could top code or deflate extreme values to make sure you do not over-value the nonlinearity. Or, you may want to adjust your values as the draft progresses (you can also do this in a simple fashion, by focusing on the player, within a value tier, who addresses your weakest cats best.

But, you do want to be careful. Even if Ellsbury has little value to you, at mid season, he may be very valuable to someone else. Don't ignore that each player has market value, even if their value to you is less.
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Re: Stolen Bases and Diminishing Returns

Postby Pokey » Mon Feb 15, 2010 1:09 pm

Thank you all very much. This is helpful stuff! ;-D
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