Similarity scores represent how closely a player's stats compare to those of other players (see source). Career similarity score for batting is used here only for non-pitchers.
Four HOFers have two non-HOFers with the same similarity score (separated by commas). Six HOF players have no non-HOFers in their top 10 list of similar players (BB Reference doesn't list more than 10): Cap Anson, Dan Brouthers, Nap Lajoie, Tris Speaker, Honus Wagner, and Paul Waner. Years listed are the first and last of the non-HOFer's career (or just the first if they are active). Team listed is the one on which the non-HOFer played the most games. See first comment for team/franchise abbreviations.