For the past several years, the winter of 2018-19 has been billed as the biggest baseball free agent bonanza in a long while, but for the second straight year, major league clubs are showing that they are far more hesitant to pay out nine-figure salaries to players whose peak years are, by and large, behind them. What was supposed to make this year different was the unprecedented arrival at free agency of two star players, Bryce Harper and Manny Machado, who reached the majors at such a young age that despite their six-plus years of service time they both just completed their age-25 seasons. Given what we now know to be true about the aging curve, this of course means that both players theoretically have several of their very best years immediately in front of them, and both at this point in their careers are on track towards building Hall of Fame careers. Baseball-Reference's similarity score rater through age 25 has three inner-circle Hall of Famers (Ken Griffey Jr., Frank Robinson, and Eddie Mathews) and two certain future first-ballot inductees (Mike Trout and Miguel Cabrera) among Harper's top ten player comps, PLUS Andruw Jones, who was a Hall of Fame talent through age thirty before injuries and poor conditioning short-circuited the back end of his career. Machado's comps through the same age also include three Hall of Famers (Ron Santo, Cal Ripken, and Griffey) in addition to Jones and future no-doubter Adrian Beltre, who additionally rates as Machado's best year-by-year comp for five of his six MLB seasons (Santo is the other). Interestingly, Harper shows up as one of Machado's age comps (sixth), but the reverse is not true. Very rarely in the forty-odd years of free agency have any players this talented and this young hit the open market, and two of them doing so at the same time has never happened. All of this is quite familiar to most serious baseball fans, but it bears repeating for the more casual fans out there.
