The loss snapped a 10-game road win streak.
Before the late excitement, the Red Sox’ only extra-base hit came from Jahmai Jones, who led off the game with a double.
Their first run came via Wilyer Abreu’s two-out RBI single in the eighth.
The biggest moment of the game immediately followed. With two runners on, Ceddanne Rafaela, the hero of Monday’s series-opening win, stepped up as the potential go-ahead run against lefthander Hogan Harris, the Athletics’ closer.
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Harris threw three consecutive fastballs. Rafaela swung and missed at each, including a half-hearted attempt at the last one, which was at least level with — perhaps over — his head, in addition to outside.
Rafaela met a better fate the night prior, when he lofted what he thought was an inning-ending popout to left field. It carried and carried until it ended up going over the wall for a grand slam, the only run-producing swing for the Sox.
The Athletics entered Tuesday with a 6.49 ERA at Sutter Health Park, which would be the seventh-highest home mark in major league history (and the highest non-Coors Field ERA since the 1930 Phillies had a 7.18 ERA).
The latest tallies for the Sox: They have lost just three of their past 21 games (and five of their past 28). They are 55-51 overall.
In a matchup of rookie lefthanders, the Sox’ Jake Bennett and Athletics’ Gage Jump were about equal — for most of the night.
Bennett lasted 6⅓ innings and wound up allowing three runs. Two came on his final pitch: No. 9 hitter Brian Serven’s home run to straightaway center field.
It was Serven’s first long ball in the majors since 2022 (64 games).
Prior to that, Bennett had been extremely efficient — again — and worked around the Athletics’ five hits. He walked two batters, one in each of his last two innings.
Since returning to the majors last month, Bennett has issued just seven walks in nine games.
Bennett struck out four.
Jump, who entered the year as a consensus top-60 prospect, tossed six scoreless innings, scattering three hits and four walks while striking out seven. He lowered his season ERA to 4.00 (12 starts) and his July ERA to 5.87 (five starts).
For the Red Sox, the early innings were all about missed opportunities. They put seven men on base through five frames — including multiple runners in each of the first two. But none reached third base, and the Sox were hitless in four at-bats with runners in scoring position.
A big piece of that plight: a pair of inning-ending double-play grounders, off the bats of Abreu (with two runners on in the first inning) and Willson Contreras (one on in the third).
After the gaggle of runners, Jump settled in over the back half of his outing, retiring nine of his final 11 hitters — with one of the exceptions being Jarren Duran, who bunted for a single but was picked off/caught stealing second base in the fifth inning.
The Sox had another shot in the seventh, against reliever Luis Medina. Rafaela led off with a single and moved to second on Caleb Durbin’s sacrifice bunt. With two outs, Andruw Monasterio smacked a deep fly ball to center that was caught on the warning track.
Tim Healey can be reached at timothy.healey@globe.com. Follow him @timbhealey.