Bryce Harper is hitting .287 with 12 home runs and 23 RBIs this season.

The Nationals’ Bryce Harper and the Orioles’ Manny Machado are already playing well beyond their years.

The two 20-year-olds are either first or second on their teams in batting average and runs scored. In most cases, prospects spend considerable time in the minor leagues before being called up, but Harper and Machado are making an impact in the big leagues before turning 21. With Washington and Baltimore in the middle of the annual Battle of the Beltways, let’s look at the two stars likely to fuel this series for years to come.

Harper’s Defining Traits

Relentless attitude: Harper attacks each game like a football player. Unfortunately for the youngster, that’s led to numerous injuries, including his most recent bout with bursitis in his left knee. He’s expected to miss the rest of the series vs. the Orioles. Harper’s been praised for his all-out hustle, yet criticized at times for putting his health at risk.

Noticeable swing: Not many players in the game today have a swing like Harper’s, which has been compared to legendary slugger Babe Ruth’s. Harper has a slightly open left-handed stance, with his bat cocked behind his ear. His swing can vary depending on the pitch, and he can hit with power and precision.

Attacking early in the count: Harper doesn’t like to waste much time when he gets to the plate and sees something he likes. When swinging at the first pitch, Harper is batting a staggering .519, and 14 of his 43 hits this year have come on the first pitch.

Machado’s Defining Traits

Proving he belongs: Harper and 21-year-old Angels outfielder Mike Trout have garnered tons of attention since taking the majors by storm in 2012. Machado was an afterthought when he was called up last August. Now, it’s a different story. The Orioles third baseman has a better batting average (.335) than Harper (.287) and Trout (.304).

Attention to detail: Machado is a perfectionist at the plate and in the field. Even during pregame warmups, he makes a point of throwing to the same spot, kicking the dirt when he misses. That kind of work ethic has led to a .981 fielding percentage, the sixth- best among third basemen in the majors.

Mr. Clutch: When the pressure’s on, Machado comes through for his team. He has a .474 batting average with runners in scoring position and two outs. He’s also critical to the Orioles’ success, hitting .363 in Baltimore’s wins compared with .300 in losses.