A dizzying 13-run eighth inning, along with a career-high eight RBIs (grand slam, three-run homer, single) from Rafael Devers, helped the Red Sox to a 19-5 walk-in-the-park victory over the Orioles in the first game of Friday’s day-night doubleheader at Fenway Park.

The romp helped soften the blow of an injury to the Sox’ best all-around player, Alex Bregman, who left the game with right quad tightness, an injury he appeared to incur while rounding first base on a fifth-inning single.

After a lackluster start from starter Brayan Bello and the lineup, the Sox’ offense cleared its throat with a five-run sixth inning.

Then their flux capacitor kicked in in the eighth, when 16 plate appearances accounted for 13 runs off of Orioles infielder-turned-reliever Emmanuel Rivera.

Abraham Toro, who replaced Bregman at third base, pitched the ninth inning for the Red Sox. He allowed two runs.

The 13 runs marked the Red Sox’ biggest single-inning surge since they scored 14 runs in the first inning against the Marlins on June 27, 2003.

The win evened the Red Sox’ record to 26-26.

The Red Sox started Lucas Giolito in the nightcap.

The Sox’ offense had tallied just four hits, all singles, in the first five innings, before coming alive in the sixth.

Nick Sogard was the first of six Red Sox batters to reach base in the sixth, with a double off fresh reliever Seranthony Dominguez.

After a walk from Kristian Campbell, No. 9 hitter Ceddanne Rafaela and then Jarren Duran knocked in a run apiece with singles, before Devers’s drive to right field.

The Orioles scored twice off Bello in the third inning, when four runners reached on three singles and a walk.

Bello was done after four innings, using up 87 pitches for the 12 outs. He allowed six hits — five singles and a double — and the two runs with one walk and seven strikeouts.

The start marked the shortest of the season for Bello and the latest in a downward trend. He has either not reached or completed the fifth inning in his last four starts after doing so in each of his first three starts.

The Red Sox scored a run in the fourth inning on Sogard’s fielder’s choice RBI.

Good defense from both clubs marked the early stages of the game.

In the second inning, Red Sox center fielder Rafaela sped back into the triangle to track down Ramon Urias’s line drive, reaching back for the catch as he dived to the ground.

In the bottom half of that inning, Orioles right fielder Heston Kjerstad denied a home run by Carlos Narvaez, snagging a line drive over the top of the Red Sox bullpen fence.

Heading into the night game, the Red Sox carried a 4-3 record on this 10-game homestand.

Michael Silverman can be reached at [email protected].