SCOTTSDALE, Ariz. >> The San Francisco Giants hope to lean on a trio of young arms to round out their rotation. That is, if they make it to Opening Day.

It was revealed Tuesday that Tristan Beck had been scratched from his start the previous day — replaced by Mason Black — and flown back to San Francisco to be examined by doctors after experiencing soreness in his right hand.

Beck, 27, is already the second member of the projected starting five to be sidelined this spring, joining Keaton Winn, who just resumed throwing on Monday after being shut down for a week with elbow soreness.

“There’s a level (of concern),” Melvin acknowledged. “What level, I’m not sure yet.”

There’s enough ambiguity with both starters that each could be ready for the regular season, but their early health issues also raise the possibility of the Giants breaking camp without two-fifths of their projected starting rotation and not much depth behind them.

Beck will undergo tests to attempt to determine the cause of the soreness in his throwing hand, which has been a lingering issue, Melvin said.

“It’s been bothering him a little bit for a while,” Melvin said. “He’s kind of been pitching through it a bit. It just got to a point where we want to find out exactly what it is, and we don’t know what that is yet.”

Winn threw off flat ground from 75 feet on Monday and was expected to progress to 90 on Tuesday. If the soreness doesn’t crop up again, the expectation is that the 26-year-old righty will be ready for Opening Day, if only stretched out to 70 or 80 pitches.

But while Winn was cleared by doctors, it was the second time he has experienced elbow soreness since being called up last season. The issues were different, Winn explained, with last year being a case of overuse and this spring ramping up velocity too rapidly, but nevertheless multiple elbow injuries are worrisome.

“With Keaton coming back, we still feel like there’s time for that,” Melvin said. “But you go through these things in spring training. Probably would be good if we didn’t have any more, but yeah.”