The win snapped Arizona's six-game losing streak and kept the last-place D-backs from being officially eliminated in the National League West race.
"That was an easy one," D-backs manager A.J. Hinch said with a smile. "Yeesh. I think the whole NL West might have been watching that game at that point. Man, it feels good to come out on top especially with as many execution issues we had early in the game. That game felt like a 7-3 game that we won, 4-3. It was pretty exhausting, but a great way to go into the off-day."
Pinch-hitter Gerardo Parra led off the bottom of the ninth with a little chopper to the third-base side of the mound that pitcher Ramon Troncoso threw past first baseman James Loney to allow Parra to reach second.
Trent Oeltjen pinch-ran for Parra and moved to third on a sacrifice bunt by Ryan Roberts. The Dodgers then walked Stephen Drew and Justin Upton to load the bases for Reynolds, who was 1-for-3 with a walk to that point.
"They're just setting up for the double play, I'm sure, and [Upton] is a little more of a contact guy than I am," said Reynolds, who leads the Majors in strikeouts with 190.
The Dodgers pulled in their infield and outfield in hoping to cut down the runner at the plate.
"I'm just trying to put the ball in play," Reynolds said. "I look up and see their outfield is pretty much playing in the infield and I know all I have to do is hit a fly ball. I just fouled off some tough pitches and was able to work a good AB."
Troncoso got ahead of Reynolds 1-2 and then just missed outside with the fourth pitch of the at-bat. After Reynolds fouled off a pitch, Troncoso once again just missed outside, according to home-plate umpire Hunter Wendelstedt. Reynolds again fouled off a pitch and Troncoso followed by missing outside for the walk.
"Some of them were close," Reynolds said. "He was throwing that sinker and trying to run it back over the outside corner. They were close, there's no doubt, but they were off and you've got to credit the umpire for seeing that. I laid off some tough pitches and we got the win."
All eight of the pitches during the at-bat were fastballs.
"When you talk about executing at-bats, that's when all the marbles are on the table," Hinch said. "So to be able to have the best plate discipline of the night for him is great, obviously. He had a couple of pitches that I thought he was going to put in play, but to fall behind, get two strikes, foul off a couple pitches and end up drawing the walk...it's a pretty unique walk-off to be able to walk."
Reliever Juan Gutierrez (4-3) got the much-deserved win.
The right-hander came in to face Manny Ramirez with the game tied and runners on first and second in the eighth inning. Gutierrez struck Ramirez out on four fastballs, the final three of which registered at 95 mph.
Loney, who along with Ramirez homered earlier in the game, then came to the plate and Gutierrez fanned him on three pitches.
"He went right after Manny and threw some gas by him," Hinch said.