Bryce Harper went 2-for-4 against Baltimore on Sunday, with a double off Jake Arrieta. Since making his major-league debut on April 28, his BA/OBA/SLG line is .286/.367/.497 in 50 games.
Mike Trout went 2-for-5 against the Dodgers on Sunday, reached on an error and stole his 21st base, adding to his American League lead. Since getting called up to the majors and joining the Angels lineup for the first time this season on April 28, his BA/OBA/SLG line is .338/.399/.531 in 51 games.
I'm sure it's not news that Harper is 19 years old and Trout is 20.
It might be surprising that only seven players under 21 have had seasons with a slugging average higher than Trout's .531 in 200 or more plate appearances. Five are Hall of Famers: Mel Ott, Ted Williams, Frank Robinson, Jimmie Foxx, and Al Kaline. Another, Alex Rodriguez, almost certainly will be. The one outlier is Bob Horner.
Just two hitters, Ott and Tony Conigliaro, posted seasons with slugging averages better than Harper's .497 in 200 or more plate appearances before turning 20. Only 12 did it before 21: Trout's seven, plus Mickey Mantle, Conigliaro, Orlando Cepeda, Vada Pinson and Giancarlo Stanton. That list includes two more Hall of Famers.
Looking beyond power to incorporate the ability to get on base, we can turn to the invaluable Baseball-Reference.com Player Index to find the best seasons of OPS (on-base average plus slugging) for players so young.
Some 22 players have had an OPS better than .800 in a season of 200 or more plate appearances before age 21. Trout's .931 ranks seventh; Harper's .865 is 12th. Conigliaro, Pinson and A-Rod are the non-Hall of Famers ahead of them.
(An aside: If you've ever wanted to play with a searchable database of baseball statistics to see what interesting questions you could devise and answer, you owe it to yourself to subscribe to Baseball-Reference.com's Player Index. It will be the best $36 per year you've ever spent.)
The more inclusive comparisons are found in OPS+, a comparison between a hitter's OPS and that of his league, in which 100 is average - a relative statistic that keeps us from eliminating players from eras when pitching dominated. It is also adjusted for the player's home park.
Trout's OPS+ through Saturday was 160. His 2012 season so far is 60 percent better than the league's average hitter. Harper's is 132, so he is nearly a third more productive than his league's average.
The five players under 21 who had an OPS+ season better than Trout's are Ty Cobb, Ott, Kaline, Mantle and A-Rod. The 13 who've done better than Harper's 132 are those five plus Williams, Rogers Hornsby, Foxx, Robinson, Dick Hoblitzell, Conigliaro, Ken Griffey Jr. and Sherry Magee. The only hitters Harper's age who had a season even 20 percent better than league average were Ott, Conigliaro, Cobb and Magee.
Some of those hitters did not wind up among the all-time greats, but most did.
(Second aside: Conigliaro was a Boston icon who led the AL in home runs when he was 20, was hit in the face by a pitch when he was 22, missed more than a season and had his career ultimately cut short by recurring headaches and vision problems. Hoblitzell was a fair hitter in a dreadful time for hitters, and his productive 20-year-old season was the best of an 11-year career. Magee was one of the top hitters in the National League during the dead-ball era, and his career OPS+ was 137, better than those of Hall of Famers Griffey, George Brett, Kaline, Billy Williams, Cepeda, Al Simmons, Tony Gwynn, Joe Morgan, Wade Boggs, Rod Carew, Dave Winfield, Carl Yastrzemski and Roberto Clemente, to name just a few.)
The last time there were two hitters who were so good so young was - actually, it was just two years ago, when Jason Heyward and Stanton each had an OPS over .830 for the season.
Trout and Harper have had 233 and 215 plate appearances respectively. Two hundred plate appearances is barely a third of a season. A lot of high averages head south as the season grinds on.
For now, however, they're playing at a historic level for their age. Stardom is never guaranteed, but it's certainly suggested by the company they're keeping.