Reynolds hit a two-out single to left in the bottom of the ninth that scored Justin Upton for the winning run as the D-backs beat the Padres, 6-5, on Monday night in front of 17,528 at Chase Field.
The victory was the third in a row for Arizona.
"Three in a row feels good," D-backs manager A.J. Hinch said. "We've put together a little momentum streak that is fun. Music is playing in the clubhouse, guys are smiling, there's a little more bounce in our step. It wasn't always easy today, but we found a way to hang in there and come back."
For a while it looked as though the D-backs might be headed towards a frustrating defeat, something that has been an all-too-frequent occurrence for them this year.
After grabbing a 3-2 lead on Upton's two-run blast in the third inning, the D-backs watched the Padres tie things up in the fifth and take a 4-3 lead in the seventh on a double by Kevin Kouzmanoff.
For good measure, San Diego "stole" a run in the eighth to go up 5-3 when Everth Cabrera drew a two-out walk, stole second and third, and then scored when catcher Miguel Montero's throw sailed into left field.
In the eighth, though, with one run already in and two outs, Chad Tracy hit a pinch-hit homer into the pool area in right-center field to tie the game.
"I was looking for a fastball [down the] middle, and he gave me a fastball-middle," Tracy said.
Tracy was 0-for-12 on the team's recent road trip and said the struggles had caused him to lose sleep and weight.
"I'm finally going to sleep tonight," Tracy said just before exiting the clubhouse.
In the ninth, Padres reliever Cla Meredith retired the first two hitters he faced before walking Upton on four pitches.
"I got the two quick outs," Meredith said. "I got to Upton, and in the back of my mind I didn't want to let one guy beat me. And I lost my aggressiveness. A two-out walk, that's not what you want to do."
Upton proceeded to steal second, and later in Reynolds' at-bat, the slugger hit a 2-2 slider into the left-field corner for the win.
"I had Reynolds where I wanted him," Meredith said. "I threw him a decent pitch, a slider he gets out on a lot. He didn't get out on that one."
No, and it turns out it was a scenario Reynolds and Upton had gone over in advance.
"Actually, me and J-Up talked in the dugout, and he said if he got on first and I had a ball on me, he was going to steal," Reynolds said. "First-pitch ball and J-Up stole. I got a hit, and that's kind of what we planned out in the dugout. It's pretty cool."
Reynolds thinks a trip to St. Louis for next week's All-Star Game would be cool, and he's certainly made a case for himself in the past few days.
First, there was the now-infamous postgame rant following an embarrassing loss in Colorado last Friday in which Reynolds called out teammates for a lack of effort.
Then Sunday, just hours after finding out he was a candidate for the Sprint Final Vote, Reynolds launched a three-run homer that broke up Jorge De La Rosa's no-hit bid and helped the D-backs beat the Rockies, 4-3.
"Mark Reynolds is helping us win, I'll tell you that much," Hinch said. "What he's done the last couple of days is what he's done all year."
Steve Gilbert is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.