We're a little over a week away from the end of the regular season, with all the feels that come with it. Excitement for the postseason, obviously, but also lingering malaise with the realization that the offseason is coming. But we'll have plenty of time for that soon enough. The time is ripe, however, to go ahead and take a look at what is probably the most successful trade of the season (with the benefit of hindsight).
First, though, a caveat. Obviously, we can't say for sure what will happen with the fates of the prospects who moved before the deadline. There could certainly be a Jeff Bagwell in there somewhere, but we have to go by what we have right now to assess the prospects who moved. That being said, no team did more to upgrade their roster and improve their postseason prospects, and at so little a cost, as the Diamondbacks did when they acquired J.D. Martinez.
Since his first at bat as a Diamondback on July 19, Martinez has been one of the best players in baseball. Since that date, he's hit 25 home runs, just two shy of The Mighty Giancarlo Stanton over the same period, and more than any San Francisco Giant has on the year. His slash line is .282/.351/.713, for a 161 wRC+, which is 11th in MLB. His 1.064 OPS is 4th best in MLB and his .431 ISO is 2nd in MLB (as is, unsurprisingly, his 49.3 Hard%).
Prior to the trade, left fielder Yasmany Tomas was having another year of defensive issues as well as problems at the plate, hitting .241/.294/.464 for an 89 wRC+ and racking up 0.1 fWAR through 49 games. Tomas succumbing to injury made some sort of a move a necessity, and bringing in Martinez allowed them to move David Peralta (.294/.348/.446, 104 wRC+) to left field, filling in a black hole in the D-Back's lineup.
The package that went to Detroit was a trio of infield prospects in Dawel Lugo, Sergio Alcantara and Jose King. Lugo was the biggest piece moved, and he was rated the 4th best prospect in Arizona's system going into the season. The 22-year-old just squeaked in at 200 on Minor League Ball's John Sickels' Top 200 List before the season. The return didn't exactly inspire much in the way of awe from the pundits, and rightly so. They got the best bat on the market, even if he was a rental, without giving up their top prospects.
Obviously, there's a serious shifting going on in terms of how teams are evaluating needs before the trade deadline and, in particular, what they are willing to give up for rental impact bats. While there were plenty of teams that could have used Martinez in their lineup, there weren't a lot of teams in dire need of Martinez approaching the trade deadline and teams weren't going to give up their most valuable prospects for a player who didn't offer anything past this season in terms of team control.
The Diamondbacks took advantage of a weak market for Martinez and got him for a relative song. Perhaps the best news for Arizona, now that their magic number is three and they are almost certainly going to make the postseason, has to be that Martinez hasn't shown any sign of slowing down just yet. In September, his 1.4 fWAR is second in MLB for position players and he leads all position players in WPA with 1.48. While Win Probability Added is certainly not a predictive stat, having the player who's contributed most to winning games in September is probably not a bad thing when October rolls around.
The biggest story of the year for the Diamondbacks has been the dominance of their starting pitching. With a 3.52 ERA (2nd best in MLB after the Dodgers) and 19.1 fWAR (2nd best in MLB after the Indians, obviously), that's understandably been the biggest reason they are in the mix for the postseason. It's easy to forget, now that Arizona has a six game lead on Colorado (who was also supposedly considering Martinez) for the first Wild Card spot, that when the the trade went down, Arizona and Colorado were seemingly neck and neck the whole season. The Martinez trade helped them create some separation in the standings as much as any one player can, now we just have to see if he can make a difference for Arizona in the postseason.