Similarity scores are intellectually intriguing, but I've never bought into their predictive value one iota, particularly for sports like football with such small sample sizes.
I agree with this.That said, similarity scores are used by
everybody in fantasy football, just not necessarily as empirically as I'm doing here. It's just like how everyone uses VBD to some extent, even if they call it their gut (long before Joe Bryant, people didn't draft kickers and TEs early).
If I said that Ryan Grant was going to be the next Tomlinson, Peterson or Barry Sanders, someone would probably bring up that those guys were top five picks and Grant was undrafted. If I said that Ryan Grant was going to be the next Willie Green or Julius Jones, someone would probably bring up that Grant's YPC was a yard ahead of those guys. If I said Grant was going to be the next Earl Campbell, someone would say he didn't have anywhere near as many carries. If I said Ryan Grant was going to fall off the face of the earth like Shaun Alexander last year, someone would say that Grant isn't anywhere near as old.
Age. Experience. Touches. Production. Draft Status. Those five things are the bulk of what makes up a player's fantasy projections. If I told you RB X was 24 years old, he started last year, had 300-1000-8 with 30 receptions, and was a fourth round rookie last year, you would intuitively have a good feel on how to project him. Obviously questions about his situation are important, but those are actually pretty easy to answer once you know the real player. Now if I told you he was 28, or a first round pick, or had 1500 yards, your projections would change significantly. That's all similarity scores are doing.