Arizona Diamondbacks’ Carson Kelly is doused after hitting a walkoff single to defeat the Boston Red Sox in a baseball game, Saturday, April 6, 2019, in Phoenix. (AP Photo/Rick Scuteri)

PHOENIX — Carson Kelly watched teammate Eduardo Escobar get thrown out at home plate on Nick Ahmed’s hit in the bottom of the ninth inning. Kelly was on deck, and the play served as motivation for the Arizona Diamondbacks catcher.

Kelly then drilled a single into the left field corner, scoring Ahmed with two outs to lift the Diamondbacks over the struggling Boston Red Sox 5-4 on Saturday night.

“You want to get it done even more. Nick did a great job. We were that close,” Kelly said. “It gave me that little extra boost to maybe hit it over the third baseman.”

Boston has dropped three straight and is 2-8 overall, a lousy start to its World Series championship defense.

Colten Brewer (0-1) allowed consecutive singles to Escobar, Ahmed and Kelly in the ninth. Right fielder Mookie Betts threw out Escobar at home on Ahmed’s hit, but Kelly’s liner to left allowed Ahmed to score easily.

Ahmed had taken second on the throw home from Betts.

“I thought I threw some good pitches in there, but they were ready for them, I think,” Brewer said. “I threw (Kelly) a two-seam in and he just turned on it.”

Kelly had two hits and three RBIs. The game-ending hit was the first of his career.

“Your heart stops when you have a runner thrown out at home plate … but that didn’t stop us,” Diamondbacks manager Torey Lovullo said. “I was really proud the way we kept pressing on.”

Greg Holland (1-0) pitched a scoreless inning for the win.

The Diamondbacks led 4-3 after two innings, but neither team scored again until the seventh. Jackie Bradley Jr. drew a leadoff walk against Yoshihisa Hirano and went to third on J.D. Martinez’s pinch-hit single. Andrew Benintendi drew a walk, and Betts drove in the tying run with a sacrifice fly.

The Red Sox loaded the bases against one of Arizona’s top relievers, Archie Bradley, but he got Xander Bogaerts to ground into an inning-ending fielder’s choice.

Boston starter David Price worked six innings, allowing four runs and seven hits with four strikeouts.

Luke Weaver improved from his last start for Arizona, giving up three runs, five hits and two walks with four strikeouts over five innings. Weaver yielded four earned runs in 4 1/3 innings against the Dodgers on March 30.

The Red Sox scored the game’s first three runs in the second. Bogaerts led off with a walk and went to third with heads-up baserunning on a single to shallow center by Rafael Devers. Eduardo Nunez’s groundout scored Bogaerts, and one out later, Devers came home on Price’s single past first base. That was Price’s first career RBI and his fourth hit in 50 at-bats.

Benintendi hit a ground-rule double to center field, scoring Christian Vazquez to make it 3-0.

The Diamondbacks took the lead in the next half-inning. Ahmed singled in David Peralta from third base with one out, and Kelly followed with a two-run double. Adam Jones singled in Kelly, who crossed home before a close play on Jones at second base. Jones was first called safe at second, but the Red Sox challenged and the play was reviewed and overturned.

“That’s been one of my Achilles’ heels for a lot of my career, having that one tough inning, and it cost me a ballgame,” Price said. “We just need to get back home, and our fans will remind us how good we are.”

Red Sox manager Alex Cora tried to keep things positive.

“It’s not perfect right now, obviously, but the quality of the at-bats were better today,” Cora said, vowing the defending champs will be fine. “They kept fighting. … There’s no frustration. We just keep grinding.”

ROOF IT

The retractable roof at Chase Field opened with no problems as the top of the fourth inning got underway. The roof malfunctioned Friday during the Diamondbacks’ home opener.

TRAINER’S ROOM

Red Sox: INF-OF Brock Holt and LHP Brian Johnson were placed on the 10-day injured list. Holt has a scratched cornea in his right eye, and Johnson has left elbow inflammation. … INF Tzu-Wei Lin and RHP Marcus Walden were called up from Triple-A Pawtucket. Lin grounded out as a pinch-hitter in the ninth.

Diamondbacks: LHP T.J. McFarland (shoulder) threw 20 pitches in a simulated game and Lovullo was encouraged. … RHP Taijuan Walker is set for a 40-pitch bullpen as he comes back from elbow surgery a little less than a year ago.

UP NEXT

Diamondbacks RHP Merrill Kelly (1-0) is set for his second start of the season Sunday against Boston. He allowed three runs in six innings at San Diego to earn the win. Cora said RHP Hector Velazquez, who has appeared in three games as a reliever this season, will start for Boston.