The St. Louis Cardinals and Arizona Diamondbacks linked up for a blockbuster four-player trade on Wednesday, with first baseman Paul Goldschmidt coming to St. Louis in exchange for catcher Carson Kelly, right-handed pitcher Luke Weaver, and infielder Andy Young. (A draft pick also swapped hands.)

The deal ought to help the Cardinals close the gap between themselves and the Chicago Cubs and Milwaukee Brewers in the National League Central. As for the Diamondbacks, trading Goldschmidt confirms they're rebuilding. That was already their suspected route, given Patrick Corbin and A.J. Pollock's free agencies, but it's nice to receive confirmation.

It's also nice to receive validation, so let's provide it by dishing out a grade for both sides.

St. Louis Cardinals trade grade: A

What is there to not like about this from the Cards' perspective? Goldschmidt is a consistent offensive force. He started last season slow, but still finished the year hitting .290/.389/.533 with 33 home runs. His career averages, for reference, are .297/.398/.532 with 31 homers. You could call him a machine, although Cardinals fans already gave that moniker to a different first baseman.

Goldschmidt should enable the Cardinals to move Matt Carpenter across the diamond to third base, which in turn gives St. Louis more options. Do they use Jedd Gyorko off the bench, or do they install him at second base? What about weighing trade options for him? There are plenty of possibilities for the Cardinals to consider between now and next season -- and nearly all of them make St. Louis a better ballclub.

If there's a downside here, it's a slight one and it's that Goldschmidt has just one year of team control remaining. The Cardinals figure to take a run at extending Goldschmidt before he hits the open market, but they'll need to be cautious. He'll turn 32 next September.

Whatever happens there, Cardinals fans should be pleased -- their team just landed one of the best first basemen in baseball in exchange for depth pieces.

Arizona Diamondbacks trade grade: D

The market is the market and so on and so forth, but this package just feels too light to be enough for Goldschmidt -- even if it is just one season's worth.

Kelly has the chance to be a starting backstop thanks foremost to his defensive chops. He's athletic (he converted from third base earlier in his career), he has a strong arm, and he's regarded as a field-general type who can handle a pitching staff. His offensive output is more uncertain, but an average stick would make him more than worth the lion's share of playing time.

The rest of the deal is where things fall apart for us. Coming out of Florida State, Weaver was supposed to have a well-above-average changeup that paired nicely with his fastball and overshadowed his inability to spin the ball. Yet the changeup didn't fool batters last season, and he's been worse against lefties for his career. Without a high-grade cambio, it's hard to see Weaver sticking in a big-league rotation for long. 

Young, meanwhile, has nice numbers but is considered more of an organizational player than a prospect worth keeping an eye on.

Arizona has a good front office. It's possible they see things we don't with both Weaver and Young. But, from our perspective, it would've been nice to see the Diamondbacks get one more piece that was closer to Kelly's level.