Projection System Life Hacks

It’s never too early to prepare for next season, just as you can never have too many articles about the mechanics of projection systems. Well, ok, the second part of that statement is a lie, but it has been awhile since we’ve talked about how we use projection systems.

Our 2016 Steamer projections are already live on all relevant player pages. You’ve probably noticed us referencing them while evaluating various catchers, first basemen, and second basemen. We’ll continue to do so as we move into third basemen this week.

When I see criticism of projections, it usually comes as some variation of “it got Players X, Y, and Z completely wrong.” As projection users, we have to understand that Steamer and other systems are estimating a range of outcomes. We then represent that range with a single statistical line.

The range of projections should follow a standard bell curve. In other words, a player should almost certainly perform within three standard deviations of their projected line. A standard deviation is different for every player due to inconsistent sample sizes. We’ve seen more of Joe Mauer than Aaron Altherr.

In general, as sample size increases, the accuracy of a projection should increase too. Paul Goldschmidt is projected to be the fifth best offensive player per 600 plate appearances. We have 2,648 major league plate appearances informing that projection.

Goldschmidt features a few important qualities that lend stability to Steamer’s expectations. Entering his age 28 season, he’s still in his peak years. Over the last three campaigns, he’s posted a .400 or better wOBA with relatively consistent plate discipline and batted ball profiles.

Steamer still projects him to fall to a .390 wOBA. The decline can be summed up in two parts. First, for a player as talented as Goldschmidt, there are more ways for him to decline than improve. Also, injuries can happen to anybody. Sometimes, players play through those injuries and struggle. That player could have a temporary or permanent loss of skill. If the player lands on the disabled list, that also influences their production. Steamer tries to look at the player’s statistics as a whole, but our hypothetical injured Goldschmidt is now just ordinary Paul Schmidt.

Players with changing skill sets represent an opportunity to exploit projection systems and defeat owners who depend upon them. The difficulty is actually identifying changed players as outsiders. That’s especially true over the offseason when there are few games and misinformation abounds.

Kris Bryant is projected as the ninth best offensive player. We have 650 plate appearances informing the projections plus a brief minor league tenure. Steamer says he’ll have a 83/29/86/11/.271 fantasy line. Since we have a small sample size, we can intuit that the range of possible outcomes is much larger than it is for Goldschmidt.

In Summary

There are three points to understand:

• Projections are a single-point representation of a range of outcomes. The likelihood of those outcomes resembles a bell curve.
• A change in talent, temporary or permanent, can create arbitrage opportunities.
• Sample size affects the range of possible outcomes.

If you can internalize these three bullets, you’ll have a solid grasp on the strengths and weaknesses of projection systems. Remember, only history can possess a single truth. The present and the future can only be estimated.