I take age and league level, and to some small extent whether it's a pitcher's league or a hitter's league, into account. And then, except for top prospects, what I am looking for is "not inconsistent with having a productive major league career". For Grossman: 21 - high-A - OPS .869 22 - AA - .786 (two teams) 23 - AAA - .760 (partial season, called up to majors) 24 - AAA - .914 (ditto) So up to year 2014, IMO he was making what I would call continuous progress. Summarized as a single word, "solid". You could not rule out him being a good player. He didn't quite make the adjustment at the major league level, but he hardly stunk up the joint, at age 24. Then Grossman's 2015 was not too good. I am inclined to give any prospect a mulligan for any single season, on the assumption that you can lose a year to some nagging injury that doesn't actually put you on the DL. (Conversely, I am alert to ruling out an outlier good year too - "sorry son, you had your career year at age 21, bad timing".) If you don't cross out bad seasons, you can overlook an opportunity like Eduardo Escobar for example - remember how people questioned whether he could exceed Florimon's production at the plate, based on his most recent year being putrid? Grossman's 2016 numbers at AAA were good enough, in small sample, with some power. As a waiver pickup, he's about as good a gamble as you will get. Of course there is the larger issue of why we are bottom-feeding, but oh well.