The big baseball argument of this generation is back on.
I'm not talking about steroids, the designated hitter rule or guessing the next time Jonathan Papelbon will make a scene. I'm talking Trout versus Harper.
Back in 2011 or so, the "Who's better between Trout and Harper?" argument was quite common, and for good reason. They were two of the top prospects in baseball, both very young -- and very talented -- phenoms with bright futures. Then something happened to put that argument on the back burner: Mike Trout took a giant step forward and became the best player in baseball. Bryce Harper certainly didn't disappoint; a 122 OPS+ through his age-21 season is nothing to scoff at. But that wasn't quite up to what Trout achieved in the majors, a 28.6 career WAR (baseball-reference version) through his age-22 season. To put that 28.6 in context, that's already more than half the entire career WAR of borderline Hall of Famers such as Jim Rice or Jim Bottomley (Trout actually passed "Sunny Jim" by this year's All-Star break).
But a funny thing has happened on the way to Cooperstown: Harper's rejoined the race and rekindled the debate.
From a projection standpoint, coming into this season, there was quite a separation between Trout and Harper. Sure, the ZiPS projection system still liked Harper enough to rank him second in MLB among players under age 25, but the difference was massive, by some 40 projected WAR. By more traditional stats, ZiPS had Trout finishing with 900 more hits, 100 more home runs, 400 more RBIs ... You get the idea.
The difference, of course, was that Trout already had his huge breakout and became a perennial MVP candidate. As much as everybody liked Harper and believed he had almost unlimited upside remaining, actually taking that step makes a player a much more valuable commodity than someone who might, maybe or probably will accomplish it.
In 2015, it happened.