About 13 months ago, just as everyone was preparing for Thanksgiving, the Mariners and Diamondbacks swung a borderline blockbuster. The big name going to Seattle was Jean Segura. The big name going to Arizona was Taijuan Walker. As the trade happened, both Dave and myself wrote about how, in the end, it could end up being the Mitch Haniger trade. All things considered, Haniger had a fairly successful 2017. There’s another player in there I’m starting to like, though, and, well, my apologies to Zac Curtis. It’s Ketel Marte. I’ve really come around on Ketel Marte.

Perhaps it’s my own fault for having underestimated his talent. In my defense, though, Marte was simply a much-improved player this past season. People have asked me several times in my chats who I think could be poised for a breakout 2018. As such, it’s long past time for me to explain why Marte has captured my attention. He could be part of the Diamondbacks core for a very long time.

As you ought to understand, there are no promises to be made. I don’t know exactly what Marte is going to do. Maybe, since the end of the season, he’s discovered a passion for watercolor painting, and he doesn’t want to play any more baseball at all. He’s a human being, and our courses are controlled by the heavy hand of randomness. But if it helps, it’s not just me. While the Diamondbacks are open to the idea of trading one of their many middle infielders, it seems that Marte is untouchable. I heard that at the winter meetings, and Nick Piecoro says as much in the link.

Marte is 24 years old. He runs extremely well. He hasn’t turned that into stolen bases, mind you, but he’s turned it into some triples. He’s quick and athletic. All the usual traits for a young shortstop. But he also hit a playoff home run I haven’t been able to erase from my mind.

The home run itself was of little consequence, but Marte sent the ball screaming, which was proof of concept. And if that homer doesn’t do it for you, here’s another, loftier one, from July.

I didn’t used to think Marte had much in the way of power. Even now, he’s obviously about one Miguel Cabrera short of being Aaron Judge. Marte will never be confused for Paul Goldschmidt, but, two things have gone on. One, over the whole baseball landscape, there’s been the reality of the home-run spike, with the fences effectively becoming easier to clear. And Marte himself has developed a better and more consistent feel for the bat. Being a switch-hitter, I suppose it might make some sense that Marte took a little time to get more polished.

Marte spent a chunk of last season working on his swing in Triple-A. The idea, as has become familiar, was for Marte to generate more lift. He wound up with his lowest ground-ball rate since 2011, when he was in rookie ball, in his first year as a professional. Maybe, under previous circumstances, you wouldn’t want to encourage a player with only modest power to try to hit the ball in the air. But times have changed, and Marte’s peak power is certainly playable. He’s reached the 110 mile-per-hour threshold, and if you just focus on balls Marte has hit at least 90 miles per hour, his big-league average launch angle just improved by more than four degrees. Marte’s in the process of becoming a different hitter.

He’s also proven he can hit for contact. He can hit for contact and he can draw walks. Marte was one of relatively few players last season to finish with a double-digit walk rate, and a strikeout rate better than average. Marte, in about a half-season, had 29 walks and 37 strikeouts, and those walks weren’t simply a function of batting eighth in a National League lineup. Marte had shown the ability to walk before, and then everything got ugly in 2016. In 2017, he rebounded.

The easiest thing to do would be to just point to expected wOBA, from Baseball Savant. Marte did just take a huge leap forward. But to make it a little more complicated, I’ve broken this down into two parts. In the following plot, you see changes in expected wOBA on batted balls only, and you also see changes in K-BB%. For the former, a positive change is good. For the latter, a negative change is good. Marte is the point highlighted in yellow.

On my spreadsheet, there are 294 players. That’s 294 players who hit at least 100 batted balls in both 2016 and 2017. Marte has the seventh-biggest improvement in batted-ball xwOBA, and he also has the fourth-biggest improvement in discipline. In terms of discipline, he improved like Alex Bregman or Justin Smoak, and in terms of batted-ball quality, he improved like Bryce Harper or Jed Lowrie. Marte, last season, was probably a better hitter than his regular wRC+ gives him credit for.

And while we’re talking about Marte as a player, I should mention he’s more than his bat. Again, he’s a shortstop — that’s a premium position — and Marte just posted a positive DRS and a positive UZR. He’d been a below-average defender in 2016, in large part because of an error problem, but it seems that here, too, Marte made some gains. It doesn’t look like he has to be forced to second base, at least not yet, which makes Marte only all the more appealing.

Adequate defensive shortstop. Fast runner. Young. To go along with those traits, Marte has shown improved discipline and contact. In a sense, you could argue he just had his breakout in 2017. After all, it’s 2017 that factors into that plot just above. But I think breakouts have to include some kind of public-awareness component, and I think Marte could build on these gains over the full season ahead. He already bats with a discerning eye, and given his better-than-average big-league contact rates, I figure Marte could further improve in terms of tapping into his power. Power is already in there, but, you saw what Francisco Lindor just did. Marte has excellent bat-to-ball skills, and that gives his offensive game a strong foundation.

The Jean Segura trade was arguably the Taijuan Walker trade, which was arguably the Mitch Haniger trade. Now I’m starting to wonder if it might become the Ketel Marte trade. Though I don’t want you to dwell too much on the comparison, I could see Marte becoming Arizona’s Jose Ramirez. I wouldn’t want to trade him right now, either. Not when he might just be lifting off.