I first told you about Washington Nationals phenom Bryce Harper’s endorsement strategy about a year ago, when the 19-year-old rookie was mostly playing it cool.

At the time, Harper was still trying to prove himself and didn’t seem to have much appetite for cashing in with advertisements despite his potential.

That sure didn’t last.

In the last couple of weeks, Harper has appeared twice — nearly naked — in advertisements for Under Armour Inc.’s “boxerjock” underwear line, as first reported by The Washington Post.

Harper signed an endorsement deal with the Baltimore-based sports apparel maker (NYSE: UA) last year.

In case you couldn’t tell from the photo, kids grow up fast in Major League Baseball, and any notion that Harper should keep a low profile until he is more established on the field seems to have passed. He’s the Nats’ best hitter, after all. We can probably can count on seeing a lot more of him.