Trevor McDonald injury hampers Giants’ future rotation plans

KANSAS CITY — With little else at stake, the Giants’ primary focus in the second half will be evaluating who they can count on for next season, particularly in their starting rotation.

It’s a puzzle that Trevor McDonald figured to fit in somewhere.

But things got more complicated when the 25-year-old right-hander walked off the mound with a trainer between the fourth and fifth innings of Monday night’s 4-3 loss to the Royals.

McDonald was placed on the 15-day injured list Tuesday, with Tristan Beck called up to take his place on the roster, but his outlook wasn’t any clearer. He flew back to San Francisco, where he will undergo further evaluation. For now, the Giants diagnosed him with an elbow strain.

They expect to have a better idea by Wednesday morning.

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“You don’t want to say it’s a part of the game,” manager Tony Vitello said. “We’re planning on him just having a little bit of time off. We’ll see what we get on the reports and go from there.”

As it stands, Logan Webb and Landen Roupp look like the only sure things in next year’s rotation. Adrian Houser is under contract for 2027 but was relegated to the bullpen. Robbie Ray and Tyler Mahle will both be free agents and are strong candidates to be traded before the Aug. 3 deadline.

McDonald debuted with one appearance late in 2023, impressed with two strong starts last September and seemed to cement a spot in the big-league rotation this season.

At his best, Vitello said, “it literally feels at the end of the day like he won the game for us.” But his 14 starts before suffering the arm injury were too up-and-down for the Giants to know for sure that he’ll be able to hold down a rotation spot for 162 games going forward.

That was one area they hoped to see improvement from McDonald in the second half.

“The one thing I think he’s searching for is a little bit more consistency,” Vitello said. “Regardless of what he’s got in front of him, I’m sure he’ll find a way to continue to develop.”

McDonald showed what he was capable of as soon as he stepped into the rotation on May 4, striking out eight and walking none over seven two-hit innings against the Padres. He made four more starts where he yielded one run or fewer. But he also failed to complete four innings four other times, including twice when he was lit up for seven or more runs.

The totality produced a 3-7 record with a 5.12 ERA, a 4.27 FIP, 57 strikeouts and 35 combined walks and hit-by-pitches in 70 ⅓ innings when he landed on the IL.

“I’ve talked to other hitters in the league. It’s a tough look,” Vitello said. “He’s a ground ball guy. Normally there’s damage that’s limited when it comes against him.”

Still, Vitello didn’t feel that he’d seen enough to commit to a rotation spot next year. After all, it remains to be seen whether that will be an option at all. While the Giants are waiting for the results of McDonald’s MRI, the combination of elbow and strain is an ominous string of words for any pitcher to hear.

Although 16 of McDonald’s 18 career appearances have come as a starter, he could be an option as a bullpen piece, something the Giants experimented with during this past spring training.

“At the very least, a part of the staff,” Vitello said. “I think he’s versatile for what it’s worth. We’re talking a long way off and a lot of other people are involved in those things. But I think the bottom line is he pitches the way we want. … There’s a lot of things he can provide for us.”

In the meantime, the injury should give the Giants a chance to get an extended look at another one of their young arms. Carson Whisenhunt’s time in the big leagues so far has been limited to spot starts but the 25-year-old left-hander was already expected to get a longer-term opportunity in the second half if and when the Giants trade Robbie Ray or Tyler Mahle.

Vitello said over the weekend that he expected Whisenhunt’s next opportunity would “come at some point soon.” With McDonald going on the IL, that timeline could be accelerated.