For several years a friend and I been engaged in a running debate over the Major League viability of Ketel Marte. This might seem like a strange thing to have been doing with our time, as indeed it was, but having strong opinions on Seattle Mariners prospects (whom the organization will inevitably break or discard) is one of the few ways of staying sane in the face of the slow-burn disaster that is my favorite team.

I’m pleased to say I was the Marte admirer, as my friend — we’ll call him “Simplicio,” as is tradition in these sorts of spats — looks quite silly in the wake of his starting the 2019 MLB All-Star game. Simplicio insisted the bat was too lightweight to carry him to sustained success, even at shortstop, and his contact ability wasn’t nearly good enough to make up for the lack of power. For me he’d demonstrated enough plate discipline to get his contact skills to play even without any pop, and he had the glove at short to provide real value to a team. This year I’ve been vindicated by Marte’s transformation into ... one of the more dangerous power hitters in baseball. Wait, what?

Marte first made the majors in 2015 as a lanky 21-year-old. The Dominican had shot through the minors, but while his contact and speed were both impressive, his record and approach hardly suggested a future as a slugger. Even bafflingly optimistic reports, such as Ben Carsley and Christopher Crawford’s at Baseball Prospectus, expected Marte to mature into a little more than a useful slap-hitter:

The swing is simple; getting through the zone quickly with a slight load and very little movement before dropping into the contact zone. His hand-eye coordination is outstanding ... he’s willing to get on base via walk. There’s some natural loft from his hand drop, but his light build and lack of weight transfer makes hitting for power unlikely. He’s a borderline plus-plus runner though, so any ball hit into the gap has a chance to turn into a triple.

That is not what happened. Marte had a strong debut season, but his productivity collapsed in 2016, and the Mariners dumped him on the Arizona Diamondbacks as part of the endlessly fascinating Jean Segura trade. But during his three years in Phoenix, he reinvented himself. As of this writing, Marte is currently hitting .310/.363/.563, with 21 home runs. His slugging percentage is 10th in the National League. In many ways, Simplicio was closer to the mark than I was — the contact and plate discipline weren’t enough to carry Marte to success. Instead, he’s become something else entirely.