Here are the six candidates, including the sole additional suggestion from Preston. I guess my selections were otherwise perfect. :) Links go to the recap of the appropriate game (some only had a brief recap, for whatever reason).
Best pitching performance: 3-0 vs. Cardinals, April 28
The Cardinals trailed only the Cubs in OPS+ among National League teams this year, and so holding them scoreless was a particularly impressive feat. Rubby De La Rosa, Daniel Hudson and Brad Ziegler combined to allow only three hits, while striking out 11 St. Louis hitters. Only two Cardinals got past first base all night. Home-runs by Chris Herrmann and Brandon Drury accounted for all three Diamondbacks runs by the end of the third inning, with that pair also scoring them all. The victory evened Arizona’s record for the season at 12-12; it was the last time that the Diamondbacks would see .500 this year.
Best all-round performance: 7-2 @ Cardinals, May 22
Per Preston: "It was probably one of the most balanced games the team played all year. Greinke had one of his best outings (game score of 74, fourth highest on the year) and the offense got to Jaime Garcia early and often in a 7-2 win. This was also the second of a string of 8 starts where Greinke looked like the player we signed. Sadly, he’d leave early due to injury in the 9th start and never find his form again. Every starter except Segura got at least one hit, and he scored two runs, one after leading off the game with a walk, and the other after reaching on an error. Bourn, Drury, Owings, and Ahmed all had multiple hits. Plus, I was at the game, so it was definitely the highlight of the year for me."
Biggest shutout: 9-0 @ Mets, August 11
Braden Shipley tossed seven shutout innings to beat Noah Syndergaard, also driving in his first major-league RBI and becoming only the third Diamondbacks pitcher since 2005 to steal a base. But the offense certainly did their share with a three-run third and a six-run fifth which blew the doors off Citi Field. Chris Owings led the way, going 3-for-5 with a trio of runs driven in, while Tuffy Gosewisch homered and added the first triple of his time in the majors. The Diamondbacks stole a total of four bases, including two by Paul Goldschmidt in the same inning; he reached base four times, on a pair of hits and two walks.
Biggest comeback: 9-8 vs. Braves, August 22
The Diamondbacks were 5-0 down by the middle of the second inning, with Zack Godley being slapped around. Arizona made a game of it, but still trailed by three runs at the seventh inning stretch. They scored four in the bottom half, with Welington Castillo’s bases-clearing double the key hit, only for Enrique Burgos to blow the save in the top of the ninth, allowing a lead-off home-run to Freddie Freeman, on a 3-0 pitch. But Goldschmidt completed the five-run comeback, responding in the bottom half of the inning with a lead-off bomb of his own, to give the Diamondbacks a walk-off win, which looked extremely unlikely in the early going.
Longest win by time: 10-9 vs. Braves, August 24
Two days later, the Diamondbacks got another walk-off win, but this time, it was Arizona’s turn to blow a five-run lead, before winning in ten innings and fourteen minutes short of five hours. After seven innings, the D-backs appaeared to be cruising to victory, with a 9-4 lead on the back of two-run homers from Jake Lamb and Goldschmidt. But the bullpen imploded in the ninth, Burgos and Dominic Leone allowing the first six Braves hitters to reach base, as Atlanta scored four and tied the game. Patrick Corbin loaded the bases in the 10th before escaping, and Lamb’s one-out double in the 11th set up Brandon Drury with a sacrifice fly chance, that he converted into victory.
Best offensive performance: 14-4 @ Nationals, September 26
The D-backs left their biggest run scoring outburst of the year late - game #156, to be precise. The bats unleashed a five-homer barrage against Tanner Roark and Washington: Jean Segura had two, and there were also long balls off the bats of Yasmany Tomas, Mitch Haniger and Lamb. Much of the damage was done off former D-back (and former near perfect game thrower against us!), Yusmeiro Petit, who was charged with five runs over his 1.1 innings. Segura ended the day with three hits, two runs scored and three RBI, while Tomas drove in five runs and Lamb scored three times. It was the most runs scored on the road by Arizona since June 2014, and only the second time since 2008 they had five homers away from Chase Field.