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May 31, 2009

Prospectus Idol Entry

Fantasy Baseball DIY: Position Player Valuation

by Tim Kniker


Hello, new readers! Welcome to our new series, Fantasy Baseball Do-It-Yourself (DIY).

Do you love fantasy baseball, but find that those annual magazines and websites don't actually help? Have you long ago left behind stodgy rotisserie fantasy for more cutting edge leagues? Are you willing to spend a little time learning to use Excel to give yourself a competitive advantage in your league? No? Well, you can stop reading now as long as you vote for me. But if the answer is "yes," we here at Fantasy Baseball DIY are going to show you how to build your own expert analysis that is optimized for your league's scoring system.

What are you going to need to build this statistical dream house? The requirements are:

  • Raw Materials: Access to the vast array of baseball information out there, especially player projection data (a Baseball Prospectus subscription will more than suffice).
  • Tools: Excel (or Access) is enough to do the trick.
  • A Little Know-How: Some basic data manipulation skills, such as how to use Pivot Tables and the VLOOKUP functions in Excel. If you don't, consider an off-season workout regimen to prepare for 2010.
  • Desire: A willingness to get your hands dirty, programmatically speaking.

Key decisions

Throughout the course of the season, the fantasy owner makes three key decisions:

  1. Whom do I draft?
  2. On a given night, who is active and who is reserve?
  3. What mid-season rosters moves do I make?

While all are important, I've been able to win leagues by simply drafting a better team at the beginning and doing the least amount of mid-season roster moves. Similarly, I've seen enough owners mess up the draft badly enough that no amount of mid-season wheeling and dealing can dig them out of the hole they have dug. At Fantasy Baseball DIY, we will cover all these questions, but, for the first few installments, we will focus on the draft.

League Context

While the techniques that we present can be adjusted to match the scoring and settings of your league (hey, that's the point of Fantasy Baseball DIY), I'm going to use my favorite league as an example. I play in a non-keeper head-to-head league of 20 teams, followed by a three-week playoff for the top six teams. We select 24 players on draft day, but, on any given night, the active roster consists of 10 position players (one at each fielding position plus two utility players) and 7 pitchers (two must be starters and two must be relievers). As for scoring, there are six offensive categories (R, HR, RBI, SB, OBP, SLG) and six pitching categories (W, SV, K, WHIP, ERA, K/BB). The selection of players is a live draft, not an auction.

Marginal Positional Value

As most fantasy baseball owners know, the key concept of player valuation is determining a player's marginal positional value (MPV) compared to other players at the same position. Although Albert Pujols has better overall numbers, his MPV (compared to other first basemen) is lower than the top players, like Hanley Ramirez, at the traditionally weak offensive positions (SS, 2B, or C).

The first step to calculating a player's MPV is to estimate the relevant stats for all likely drafted players in the upcoming year. By being a Fantasy DIYer, you can use whichever projection system you like (PECOTA, CHONE, Marcel, ZiPS, an average of many systems, etc.). There's no need to create your own projection system (unless you want to). After all, Bob Vila doesn't make his own bricks. He just uses quality raw materials from a supplier he trusts. Personally, I like combining two BP data sets, the downloadable PECOTA projections and the depth charts, which refine the expected playing time.

Note to Baseball Prospectus: a great addition for next year would be a downloadable file of the plate appearances and innings pitched used in the depth charts, preferably with the HoweID key for each player for easy joining with PECOTA projections.

Baseline Calculation

The first step in determining MPV is to calculate a baseline for each position. To do this, we take the average of each player that:

  • is eligible at that position and
  • is projected to get over 200 plate appearances.

The table below shows what we projected the baseline numbers for each position at 2009 to be:

Position   PA    R  HR   RBI  SB   OBP   SLG
  1B      519   69  20   75    3  .358  .472
  2B      461   58  10   50    9  .337  .412
  3B      445   56  15   60    5  .340  .448
  SS      441   53   8   45   10  .331  .395
   C      382   43  11   47    2  .333  .419
  RF      470   62  15   61    7  .345  .450
  CF      460   62  12   52   15  .339  .425
  LF      466   62  17   63    8  .345  .458
  Avg     453   57  13   56    8  .341  .435

Based on a team that has each position player plus two utility players (which I fill in with an average player), my baseline team stats are:

             PA    R   HR  RBI  SB   OBP   SLG
Team Total  4552  578 132  465  74  .341  .435

Examples of MPV Calculation

MPV is calculated by determining how a given player, if inserted into the baseline roster, changes the team's final statistics in each category. Let's take two examples, both third basemen, to show how to do the MPV calculation: David Wright and Russell Branyan. Based on the PECOTA projections and depth charts from late February (my draft this year was early March), the projections for each of these were:

Player     PA   R   HR  RBI  SB   OBP   SLG 
Branyan   463   61  26   75   6  .335  .491
Wright    694  119  32  106  20  .400  .538

By inserting Branyan or Wright in the baseline team's lineup and removing the "average" third baseman, we calculate the improved scores of the baseline team. As our more astute readers will notice, we are doing similar "first principles" calculations that lead to the creation of stats like MLVr and VORP, but geared for the scoring of the league, not for increasing run production in the major leagues. The table below shows the new team totals with Branyan (first row) and Wright inserted (third row). The second and fourth rows show the percent improvement in each category over the baseline.

                      R    HR  RBI  SB  OBP*  SLG*  MPV 
Team+Branyan         581  143  580  75  .340  .441
Branyan Improvement   1%   8%   3%  1%  - 2%    7%   18

Team+Wright          639  149  611  89  .350  .450
Wright Improvement   11%  13%   8%  20%  14%   18%   84

The MPV column is simply the sum of the percent increases in each of the scoring columns, since in this league each category counts equally. Also, we calculate the MPV of a player if they were inserted into the utility slot as well. As the draft proceeds and if all of a player's eligible position spots get filled, he will likely become a utility player. When this occurs, the MPV compared to the average utility player is a better player ranking.

Note that the percent improvement calculation for OBP is compared to increasing the OBP over a reasonable low-level of .275. We do the same for SLG percent as a percent increase over .350. I find that these help put these rate categories on a similar scale to the counting categories.

Personally, I also note if the MPV for a player is heavily weighted by one single category, such as SB for hitters or SV for pitchers, where the majority of points scored come from just a single player or two. A player like Jacoby Ellsbury may be overvalued, because most of his benefit will come from stolen bases. If your team also has another stealing threat (like Jose Reyes), the additional benefit of Ellsbury is not as great.

After calculating the MPV for every player, we create a sorted list for each position. In the position list, we include all players that are eligible at the position or will likely be eligible. For example, Russell Branyan was not eligible at 1B to start the season, but it was pretty certain in Spring Training that he would likely be the starting first baseman. Next to their name, we put down the MPV score for that player in that position as well as his utility role MPV. When it is our turn to select in the draft, we simply look at the top of the list of all positions and select the player with the highest MPV on any position list. See the table below for an example of the top of the lists at a few positions this year.

1B                    2B                     SS
Pujols,A.  (76,91)    Utley,C.    (59,52)    Ramirez,H. (104,91)
Berkman,L. (44,58)    Kinsler,I.  (58,52)    Reyes,J.   ( 98,91)
Howard,R.  (39,53)    Roberts,B.  (51,44)    Rollins,J. ( 72,59)
Cabrera,M. (36,50)    Phillips,B. (43,37)    Tulowitzki ( 31,18)

There are two distinct decision-making processes regarding the draft. We have discussed the first, which is the preparation before the draft which lends itself to a sabermetric-type analysis. The second is the adjustments you make as the draft unfolds. The drivers that affect your adjustments are more like a poker game which is about reading your opponents, understanding what they are trying to accomplish, and making tweaks to your own strategy to compensate. If you've done good prep work, the amount of tweaks you make will be minimal.

Next Time on Fantasy Baseball DIY

By looking at the counter in Microsoft Word, it seems that I'm out of words today. Please keep your eye posted for the next installments of Fantasy Baseball DIY, where we will:

  • Describe the MPV calculation for pitchers
  • Adjusting the MPV calculation to maximum bid prices for auction leagues
  • Incorporate team health reports and Beta values from the PECOTA projections in our MPV calculation so that we understand the risk in each of our scoring categories.

Good bye and hope to see you next time at Fantasy Baseball DIY.

Tim Kniker is an author of Baseball Prospectus. 
Click here to see Tim's other articles. You can contact Tim by clicking here

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