That mistake on Wednesday came in the 10th inning when Boxberger left a pitch too far up in the zone against Giants first baseman Brandon Belt, who launched a go-ahead, two-run homer that proved the difference as the D-backs lost to the Giants, 4-3, at Chase Field. It's just their fifth loss of the season.
Boxberger said after the game that he intended to bounce the pitch.
"Makes more sense if I walk him there, than to do what happened," he said.
Prior to Belt's homer, Boxberger hadn't allowed a run in seven innings of work this season, having given up just three hits. He'd slammed the door for a save five times.
The D-backs' bullpen as a whole was good on Wednesday, just as it has been all season. Fernando Salas, Yoshihisa Hirano and Archie Bradley each pitched a scoreless inning of relief after starter Robbie Ray gave up two runs in six innings.
The club's bullpen has allowed 14 earned runs in 17 games this year.
"That's the part of it that stinks," D-backs manager Torey Lovullo said. "Our bullpen has been lights-out, and they're going to make mistakes too and nobody is exempt from giving up runs when you make a mistake."
Unlike most times he'll pitch for the D-backs this season, Boxberger didn't have a run or two or three to work with. His job was to keep the game scoreless for another half inning and allow the bats to continue a rally that began in the eighth inning.
Lovullo's confidence in Boxberger hasn't wavered, though.
"He's our guy. He's our closer," Lovullo said. "He made a quality pitch and a good hitter made an adjustment to it and hit a two-run home run."
Boxberger said he'll just flush the mistake and move forward.
"You kind of think about it for a little bit that night, but after that, it's a new day tomorrow, new game tomorrow," he said. "I'll be back out there and hopefully in a situation to win a game."
MOMENTS THAT MATTERED Ducks on the pond: In the eighth inning, Jarrod Dyson hit an RBI triple to cut the Giants' lead to a run. However, he remained stranded at third. In total, the D-backs went 4-for-16 with runners in scoring position, including stranding potential game-winning runs in the ninth and 10th innings.
"I'm sure that these guys were seeing some good pitches and they just didn't execute," Lovullo said. "Hitting is hard with men in scoring position and less than two outs. I know the hitting coaches are relentless with talking about an approach, so I'm satisfied knowing that they are going up there prepared.
"Did they execute? No, but that's just the nature of the game. So I'm not going to be critical of their approach if I know that they go up there with a gameplan. That's all that I'm concerned about."
SOUND SMART Ray needed just three strikeouts to reach 600 for his career. He reached the mark in two innings against the Giants. It took Ray 93 starts to get there, the second-fewest of any active left-handed starting pitcher (Chris Sale needed just 82). He finished with nine total strikeouts.
HE SAID IT "His outing looked like it was more of a typical Robbie outing with nine punchouts. I know everybody is velo watching when Robbie's in the game. It looked like the velocity was climbing back to where we saw it last year, but that's not the only thing we're looking at with Robbie. He was getting some outs with pitches in different areas at different times. I thought it was his best outing of the year." -- Lovullo, on Ray
MITEL REPLAY OF THE DAY D-backs shortstop Nick Ahmed dropped a line drive from Andrew McCutchen, and though he quickly picked up the ball, his throw pulled first baseman Paul Goldschmidt off the bag. Goldschmidt swiped at McCutchen, who was ruled safe initially. Lovullo challenged the call, and it was overturned, ending the fifth inning and securing a second consecutive 1-2-3 frame for Ray.
UP NEXT Zack Greinke will toe the rubber for the D-backs in their series finale vs. the Giants on Thursday at 6:40 MST. Greinke overcame back spasms in his last start against the Dodgers, staying in the game and allowing four runs over 6 1/3 innings to earn his first win of the season. The D-backs will face Ty Blach, who holds a 4.43 ERA through four starts thus far.
Justin Toscano is an associate reporter for MLB.com.