Bryce Harper, Washington Nationals
42 home runs as a 22-year-old in 2015
Bryce Harper joined the 30-homer/22 or younger club just last season when he broke out with an amazing .330/.460/.649 season. He hit 42 jacks, the fourth-highest single season total ever for a 22-year-old (behind 1937 Joe DiMaggio, 1970 Johnny Bench, and 1992 Juan Gonzalez).
This year has been a disappointment compared to last year’s excellence. Harper currently has 23 home runs and a sub-.500 slugging percentage. He’s still getting on base at a good clip (.383 OBP), but a .261 Batting Average on Balls In Play has contributed to a career-low .251 batting average. Harper is still likely to finish the year with at least 4.0 Wins Above Replacement (Fangraphs WAR), but that’s a far cry from last season’s 9.5. He’s currently 37th in WAR for position players after leading baseball in WAR last year.
Of course, Harper is just 23 years old and has 120 career home runs with 25 games still to play this year. He could easily finish the year as high as eighth all-time for career home runs through the age of 23. He needs three home runs to pass Juan Gonzalez, Mickey Mantle, and Orlando Cepeda. If he really gets on a tear in September, eight more home runs would move him past Ted Williams.
Next: Baltimore Bomber