PHOENIX — Carson Kelly drilled a single into the left-field corner, scoring Nick Ahmed with two outs in the ninth inning to lift the Arizona Diamondbacks over the struggling Boston Red Sox 5-4 Saturday night.

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

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

Kelly had two hits and three RBI.

Greg Holland (1-0) pitched a scoreless top of the ninth.

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 took 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 Bradley got Xander Bogaerts to ground into an inning-ending fielder’s choice.

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

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

The Red Sox plated the game’s first three runs in the top of the second. Bogaerts led off with a walk and took third with heads-up baserunning on a shallow single to 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 and making it 3-0.

The Diamondbacks took the lead in the bottom of the second. 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, but the Red Sox challenged, and the play was reviewed and overturned.

ROOF IT

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

TRAINER’S ROOM

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