According to this weekend’s ESPN Sunday Night Telecast, Bryce Harper has, in recent years, often performed his pregame routine and taken batting practice indoors, in the bowels of major-league ballparks, much to the disappointment of ballhawks across America. But Harper revealed himself over the weekend in St. Louis, taking BP on the field, and any time a star like Harper deviates from a routine, it raises curiosity. During the broadcast, ESPN’s Jessica Mendoza related how she’d asked Harper about the change. He said he wanted to hit some batting practice home runs, wanted to see the ball travel.

Perhaps he wanted to see how an adjustment, something akin to an R&D prototype, would work outside a lab setting, outside of an indoor batting cage.

When I think about Harper’s swing, I think about the violence of it. The leg kick, the force compelling his back foot — his left foot — to rise from the ground. Former Nationals beat writer Adam Kilgore wrote an excellent multimedia piece about Harper’s swing for The Washington Post several years ago.

From that piece:

[Nationals video coordinator Rick] Schu scanned through video and found film of Harper hitting. He arranged clips of Harper and Ruth side-by-side on the monitor and stopped at the moment each hitter’s bat connected with a pitch. In each still picture, he saw a stiff front leg, an uncoiling torso and a back foot lifting off the ground. “Wow,” he thought. “That’s identical.” … “The full thing is God-given,” Harper said. “I don’t know how I got my swing or what I did. I know I worked every single day. I know I did as much as I could with my dad. But I never really looked at anything mechanical. There was nothing really like, ‘Oh, put your hands here.’ It was, ‘Where are you comfortable? You’re comfortable here, hit from there.’ ”

What’s interesting, at least to this author, is that Harper is willing to tinker with a gift that allowed him to reach the majors at 19. What’s perhaps troubling for the opposition is that he continues to look for ways to improve despite already possessing an NL MVP on his resume and returning close to that form thus far in 2017. He’s still just 24 — he won’t turn 25 until October — and is four months younger than Aaron Judge. His youth suggests he’s still learning himself and the game. And on the ESPN telecast, Harper debuted an apparent decision to trade power for control — or at least explore it. It’s not a swing I recall him taking — at least not regularly — a swing seemingly executed at 80% effort.

Against the hard-throwing Carlos Martinez, Harper shelved his signature leg kick. To commence his swing, he slightly raised his right foot but not completely from the ground, and took a much less explosive movement. He seemed to consciously trade power for control.

Consider Harper’s first swing of the evening:

And his second, fouling off a 99 mph fastball from Martinez:

And Harper did this in all counts, not just with two strikes. I’m not sure we’ve seen many swings from Harper that have exhibited less visible effort than the one Harper used to launch a first-inning home run on a decent pitch from Martinez.

The swing was easy, akin to a tennis backhand. Harper even kept both feet on the ground.

And if you thought that swing perplexed Martinez, how about Harper’s next plate appearance when he lifted his 20th homer of the season off a changeup that nearly scraped the ground:

Let’s pause for a moment and reflect on that location and swing ….

That was an easy swing. It wasn’t a 110 mph exit-velocity home run; it left Harper’s bat at 97 mph and with a 30 degree launch angle. But a 500-foot homer and a 390-foot homer still allow batters to circle bases uncontested. What if Harper has a new mode? What if he will gear down in situations and trade contact for power?

Nor was this just a tool Harper adopted against Martinez, who possesses a 99 mph fastball. He utilized it later in the game, too, when he flied out on a 1-1 pitch against Mike Mayers in the seventh inning.

Harper continued to employ the leg-lift-less swing into his final plate appearance Sunday, which resulted in a double off a full-count offering.

What if this loud one-game sample provided enough positive reinforcement to remind Harper he doesn’t need to hit pitches with 100% effort to remain one of the game’s best offensive performers? Perhaps Harper can produce even more value by trading power for control. He has said in the past he is guilty of overswinging.

And, hey, this looks a lot like Daniel Murphy’s beginning footwork. It’s quite plausible that Murphy’s expertise and value as a teammate extends beyond knowledge of swing planes.

Harper doesn’t have many weaknesses, but he has been much more productive with two strikes this season.

Bryce Harper’s Two-strike Production by Year Season OPS K% 2013 0.596 38.5 2014 0.490 50 2015 0.783 38.9 2016 0.618 38.2 2017 0.913 35.9

If Harper has been working on change behind closed doors, the pivot was made Sunday.

Just a day earlier, on Saturday, Harper was employing his typical leg kick against Michael Wacha, who was hitting 98 mph. He was even using a leg kick with two strikes on Saturday:

Two months earlier Harper was using a leg kick…

And on Opening Day, when Harper homered on a two-strike pitch, a 95 mph fastball from David Phelps, he was still using a leg kick…

Harper has often (almost always?) employed a leg kick since his debut…

(It strikes me as somewhat remarkable how few Nats fans were on hand to witness his first major-league homer.)

Following Sunday, Harper employed the quieter swing on Monday and Tuesday against the Mets, Harper kept his foot on the ground early against Steven Matz…

But Harper also reverted to a leg kick after a swing in his second at-bat…

On Tuesday, Harper was still committed at times to the quieter lower body…

I haven’t watched every at-bat of Harper’s career. I’m not sure if Harper has experimented much with eliminating the leg kick, but nearly all of his two-strike extra-bases hit since 2015 (at least those that are accompanied with video at Baseball Savant) have included a leg kick.

Harper’s swing, notably his hand placement, has changed over the years as he has lowered and raised his hands and tried more a relaxed starting position. We will have to wait and see if Harper is committed to this no-leg-kick approach, or if it is just a tool he uses against certain pitchers or situations. Or if it is abandoned altogether. But what it does tell us is that Harper is still learning, still experimenting — and perhaps listening — and still believes he has other levels to reach.

Harper has always had a swing of beauty, a beautiful blur of bat speed, of violence, but perhaps his evolving swing will eventually trade violence for control and produce even more production.