It's why you can do some forecasting from a player's record but it requires care and is hardly an exact science. Throw out the player's best season so far. Every player has a Career Year. Sometimes that Career Year happens at AA, and fools you. LoMo had his, last year, and to my surprise it fooled the analytics team here. Throw out the player's worst season. He was probably dinged up. Maybe throw out another bad season too, on the same grounds. More than that, and maybe dinged-up is his place in this world. What you have left, which for prospects may be only a little bit, you can try to extrapolate from, factoring in age and competition level at each step. Eduardo Escobar was the example I liked to use, back earlier in his career - he had a stinker season or two, but who knows why. The talent for a career was there. LoMo is probably somewhere between 2017 and 2018, too.