For better or worse, getting through the sixth inning Sunday against the Diamondbacks was almost a non-negotiable for Red Sox starter Tanner Houck.
The Sox have a long day ahead of them Monday with the Blue Jays coming in for a doubleheader and they need as many available arms as possible. Their decisions for the suspended game from June 26 to be resumed Monday depended on which arms they had to call on Sunday. Houck’s primary job was sparing the Sox bullpen as much as possible.
The Sox had good reason to believe Houck could eat innings. He had given the Sox at least five in each of his previous seven starts, and six each of the past three times he’s taken the mound. For his part, Houck treated the start the same as any other.
“Go out there and I’ll take the ball as long as I can — or as long as they’ll let me go,” he said. “Regardless of whatever tomorrow brings, I know that as a team we’ll kind of handle that, but we’re worried about today in the moment.”
Staked to a four-run lead early, Houck gave the Sox six innings, but the Diamondbacks stung him for six runs on the way to a 7-5 win in their series finale at Fenway.
“He was erratic today,” manager Alex Cora said. “In a game that we needed him to go deep, he went six. We’ve got a doubleheader tomorrow. We don’t have an off day. So he’s been our guy, so you’ve got to stick with him.”
The Sox were swept for the fifth time this season, and the third time at home.
Triston Casas, who said he’s been getting more and more comfortable since returning from a rib strain that cost him 98 games, gave the Sox an early lead with a solo homer in the first.
He shot a 2-and-2 fastball from Merrill Kelly to deep center field for his eighth homer of the season.
Rafael Devers stretched the lead with a three-run homer in the fourth. Kelly left a sinker dangling over the outer half of the plate and Devers shipped it to the batter’s eye in center field for his 28th home run of the season and the 200th of his career — the youngest Red Sox to reach that mark.
With a 4-0 lead, Houck was in position to coast. He gave up just three hits over his first four innings, and got a lift in the field thanks to a season-high three double plays.
But things got shaky in the fifth. Pitching coach Andrew Bailey took a trip to the mound after Houck walked Adrian Del Castillo, gave up a single to Eugenio Suárez, then walked Luis Guillorme to load the bases with no outs.
A ground out to first by Geraldo Perdomo plated Del Castillo and got the Diamondbacks on the board. A sacrifice fly to left field by Corbin Carroll scored Suárez and cut the lead to 4-2. A single by Jake McCarthy brought Guillorme around. That quickly, the Sox lead shrunk back to one.
Houck kept the edge by getting Joc Pederson to ground out to short. But no one was warming in the bullpen when Houck walked back to the dugout. His work for the day wasn’t quite done.
He came back out for the sixth, gave up a one-out single to Pavin Smith, then walked Del Castillo, putting himself in a tight spot with Suárez back at the plate, swinging the hottest bat in the series.
Suárez crushed a first-pitch sweeper into the Monster seats for a three-run homer, his 20th, and what was once a four-run Sox lead flipped to a two-run deficit.
“Suárez, he was a monster all weekend,” said Cora after Suárez finished the series 8 for 13, with two homers and 10 RBIs.
On average, the Sox have sent 4.9 pitchers to the mound each night since the All-Star break (up from 3.9 prior to the break). The Sox have had to use at least three pitchers in every game since the break. They used four Sunday.
It’s not unusual for Cora to lean on different pitchers the longer the season stretches. But Sox relievers have thrown 134⅔ innings in 34 games since the break, sixth-most in MLB.
Brennan Bernardino threw a clean seventh. Joely Rodríguez kept Arizona quiet in the eighth despite allowing two hits. Lucas Sims gave up a solo homer to Perdomo in the ninth.
The Sox are 4-10 over their last 14 home games, but Houck said the slide hasn’t rattled anyone in the clubhouse.
“Come back tomorrow, get to work, keep playing,” Houck said. “We’ve got about a month and a half still, so just keep going out there, playing hard each and every day, get your work done and just keep going, keep plugging away at this.”
Julian Benbow can be reached at julian.benbow@globe.com.