For an eighth-round pick who got less than $100,000 to sign in 2009, Paul Goldschmidt had an impressive cup of coffee with the Diamondbacks in 2011. He notched 18 extra-base hits and 20 walks in 177 plate appearances. He whiffed 53 times in that sample, too, though, so I felt comfortable (using what scouting information I had heard, not just the numbers) waving away that success on some level.

He was even better in 2012, but valid doubts lingered. He hit .286/.359/.490, and he reined in his swing-and-miss to the tune of 130 strikeouts in 587 plate appearances, but his walk rate also fell. Not only that, but he hit only 20 home runs, a fairly paltry number for a first baseman in Arizona. (He did add 43 doubles and a triple.) He also had a platoon split problem:

Paul Goldschmidt, 2012

Mashing lefties is well and good, but that bottom row is not a pretty line from a one-dimensional talent. I adjusted my projections for him somewhat, but was not ready to declare him a long-term, full-time player, let alone a star.

The season he’s having right now might not be absolute confirmation of my being wrong, but it goes an awfully long way.

Goldschmidt hit a game-winning grand slam in the eighth inning Tuesday night, his 31st bomb of the season, driving in his 100th run. Those are not the stats with which I’m concerned. Home run totals do not great hitters make, and RBI are a function of opportunity as much as talent. I also don’t want to get bogged down in the fact that that was his third grand slam, or that he also has three walk-off homers this year, or that one of those walk-offs came in a game wherein he had also homered to tie the game in the ninth inning. (Ryne Sandberg has nothing on him.)

All of that makes his season a great deal more fun, and I’m sure it’s fed what has become wild popularity for him among Arizona fans. A similar set of huge hits nestled into a terrific season made Aramis Ramirez my favorite player for a few years. It’s the big picture, though, that absolutely blows me away.

Goldschmidt is hitting .297/.393/.552. He’s striking out more than last year, but as a result of working much deeper counts: He’s walked 66 times already, counting being hit by pitches but not counting intentional passes. In 44 fewer plate appearances than he had last year, he already has three more total bases. His OPS against righties is up nearly 200 points, to .926. He’s the total package.

Strangely, Goldschmidt has also had value on the bases ever since reaching Arizona. He’s not a world-class taker of the extra base during action sequences, but he has a startling 35-for-43 mark when stealing bases in his career. For a guy who was once considered so slow-footed as to be in danger of relegation to DH-only duty, that’s remarkable.

He’s still maturing as a hitter, trying to find certain balance points. He’s hit for more home-run power in the second half, but at the cost of some of his more classic, gap-to-gap screamers. For instance, he has seven homers in August, but no doubles. He’s back to striking out about a quarter of the time this month, but only because he’s become more selectively aggressive, taking aim at the seats and contenting himself with walks (15 of them in scarcely more than 80 plate appearances) more often.

Goldschmidt is a good reminder of the value of even collegiate and minor-league numbers. The Diamondbacks clearly knew what they had, but scouts questioned Goldschmidt’s hit tool and bat-to-ball skills early on. A look at his stats should have helped soothe them, or at least forced them to admit that the power could help him overcome his deficiencies:

Paul Goldschmidt as a Professional

I won’t fault folks for not projecting the development in his approach, from a guy who struck out over a quarter of the time in the California League to one who should finish third in the NL in walks. That’s good work by either internal scouts or the player-development staff in Arizona. Still, the power was always there, and seems awfully loud to have been, if not dismissed, at least downplayed, for so long.

It’s a right-handed power hitter’s world right now. Pitchers pour in such good raw stuff, while still hitting the strike zone, that walk rates are falling even as strikeout rates explode, league-wide. Goldschmidt, like Mike Trout, Yasiel Puig, Miguel Cabrera and Manny Machado, to name a few, is a perfect guy for this era, unafraid to whiff, but eager to make pitchers pay when bat does meet ball.

I’m not sure what converging phenomena have led us here. I’m not fully satisfied by the explanation above, but it’s certainly part of it. There’s more to it, but I can’t quite put my finger down. What I can say is that Goldschmidt lives up to his sobriquet, in that, given the current state of the game on the field, he truly is America’s First Baseman.

Kevin Towers locked Goldschmidt up in late March, on a deal that will pay him $17.5 million over what would have been his three arbitration seasons (beginning 2015) and that could allow Arizona to control him for two more years for a total of $25.5 million, half of which is optional money for the final season on the contract. At the time, I was not a fan of that deal. I have to give credit where it’s due: That contract looks like a steal, a perfectly-timed maneuver at a time when executives seem to be mistiming extensions left and right.

I’ll offer just one final note of caution: As good as he’s been, Goldschmidt carries some downside risk. For one thing, whatever systemic unknown it is that so nicely suits right-handed sluggers right now, it could be gone at any time. That would not, presumably, ruin Goldschmidt, but it would set him back some. I really do believe something unseen and external has been partially responsible for his success, and for that of others like him.

For another thing, though, Goldschmidt will turn 26 before the year is out. I’m strongly inclined to read the rapid changes in his approach and skills balance over the last 1,000 plate appearances as development, but given his one-dimensionality, right-handedness and phyiscal profile, there’s a way to read it as aging. If Goldschmidt is already relying on old-player skills, by age 30, he could be an actual old player, of fading utility.

That’s for later. For now, Diamondbacks fans can revel in the huge hits, and many of my peers in the Twittersphere can delight in the game’s relentless ability to make us look stupid.