Garrett Whitlock will drop back into Red Sox rotation with a start against Diamondbacks

PHOENIX — Roughly five weeks after he landed on the injured list, Garrett Whitlock will return to the Red Sox rotation on Saturday against the Diamondbacks. As frustrated as he was to land on the injured list with ulnar neuritis in his right forearm, the pitcher recognizes that the stint was necessary.

“I think we definitely got in front of something before it got worse. I wasn’t thrilled that I had to take time away, but it’s probably best in the long run,” said Whitlock. “Now I’m back and I’m just trying to stay with the team for the rest of the year.”

Whitlock had struggled in three starts this season, going 1-2 with a 6.19 ERA. He struggled not just with results but also to capture the pitch mix that can allow him to thrive — specifically, his changeup.

Whitlock’s changeup was one of the most effective in baseball in 2021 and 2022. He held hitters to a .144 average and .240 slugging mark thanks to its anvil-like drop.

But that trait diminished, going from 35 inches in 2021-’22 to just 30 this season. With that, Whitlock missed his target, resulting in more pitches in the heart of the zone and fewer swings and misses. Before landing on the injured list, Whitlock had allowed a .400 average and .850 slugging percentage on changeups while allowing five extra-base hits on the pitch, one more than he gave up in all of 2022.

“It was too hard and it wasn’t getting the depth that it normally got,” said Whitlock. “It wasn’t getting as low as I wanted. I was starting it where I wanted, but it wouldn’t get down in the depth of it. And so those balls have gotten hit harder. So I’m just making sure I’ve got the depth on it, and also the speed differential that makes my fastball play up more.”

The injury may have impacted that signature offering. Whitlock said when he felt the discomfort, it was in the area of his forearm that he pronates while finishing the changeup.

“That is where the pain was coming from,” said Whitlock. “It’s possible my body was not wanting me to get fully there.”

But since he resumed throwing, Whitlock has been pain-free, allowing him to work on regaining his feel for the pitch. He heavily emphasized his changeup in two rehab starts for Triple A Worcester last week, with promising results. According to Statcast data, he averaged 36 and 38 inches of vertical movement on the pitch in his two WooSox outings.

“I’m still working on it, but I’m happier with where it is than it was [before the injured list],” said Whitlock.

Duvall on assignment

Outfielder Adam Duvall, out since April 10 with a distal radius fracture in his left wrist, will start a rehab assignment Tuesday with the WooSox. He will be the designated hitter for a game before playing in the outfield.

Duvall is eligible to return from the 60-day injured list on June 9.

“Little by little, we keep adding,” said Sox manager Alex Cora. “That’s good news.”

Though Duvall had stood in at first base, a position he played early in his big league career, to take throws while working out at Fenway Park recently, Cora said having him play first base this year was “not even a thought.”

Rafael Devers was 2 for 19 in the five games prior to his getting Friday night off.Ashley Landis/Associated Press

Devers sits out

Rafael Devers was out of the Red Sox lineup for the series opener with tightness in his left calf, something the third baseman experienced when awkwardly trying to dance around a tag on a failed attempt at scoring on a double-steal on Wednesday against the Angels.

“He’s day to day,” said Cora. “It felt better [Friday]. Hopefully he’s back out there [Saturday].”

Chang, Arroyo hit in minors

Infielders Yu Chang (broken hamate) and Christian Arroyo (hamstring) both started minor league rehab assignments on Friday. Chang served as DH for Double A Portland, going 0-for-3 with a pair of strikeouts. Afterward, he acknowledged discomfort when he swung.

“In my second at-bat I swung at a low slider and I felt it getting worse,” Chang told TVBS, a Taiwanese network. “So I tried a third at-bat and swung at a cutter. I feel like I might need more time. It’s all good in batting practice but I felt soreness swinging at low pitches.”

Arroyo joined Triple-A Worcester, going 1 for 2 with a walk as a DH.

Both players are expected to play in the field Saturday. Depending on how they feel, they could get another game at DH Sunday before getting re-evaluated Monday in Boston on the Red Sox’ off day.

Cora said both players are likely to need a few more games in the minors next week before they’re ready to be activated.

As for Trevor Story, he continues to add to his baseball activities in Fort Myers. While his throwing progression is the most deliberate element of his return from right elbow surgery, the team remains “100 percent” focused on bringing him back as a shortstop, said Cora.

Hazen honors wife’s memory

Prior to Friday’s game, Diamondbacks general manager Mike Hazen, formerly the GM of the Red Sox, presented a $200,000 donation on behalf of the Nicole Hazen Fund for Hope to the Ivy Brain Tumor Center, honoring the memory of his wife. Nicole Hazen passed away last year at the age of 45 from complications due to glioblastoma.

Alex Speier can be reached at alex.speier@globe.com. Follow him @alexspeier.