SCOTTSDALE, Ariz. -- The Giants got unsettling injury news concerning another member of their projected starting rotation on Tuesday.

Right-hander Tristan Beck, who appeared in line to open the season as the club’s No. 5 starter, was sent back to San Francisco to be evaluated by team doctors after experiencing discomfort in his throwing hand. Beck, 27, had been slated to make his spring debut on Monday, but the Giants decided to scratch him and have pitching prospect Mason Black start in his place.

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

Beck’s setback comes a week after the Giants briefly shut down projected No. 4 starter Keaton Winn with mild elbow soreness. Winn’s MRI exam came back clean, allowing him to begin a throwing progression on Monday. Winn, 26, was slated to throw out to 95 feet on Tuesday and has said he believes he’ll still have enough time to build up to approximately 70-80 pitches by the end of the spring.

Still, the dueling injury concerns will only heighten the uncertainty surrounding the Giants’ starting rotation, which is light on both depth and experience since Alex Cobb (left hip surgery) and Robbie Ray (Tommy John surgery) are expected to open the season on the injured list.

“There’s a level [of concern],” Melvin conceded. “What level, I’m not sure yet. A lot of it has to do with Keaton coming back. We still feel like there’s time for that. But you go through these things in Spring Training. It’d probably be good if we didn’t have any more.”

The Giants will hope for good news on Beck in the coming days, but if he ends up being sidelined for the start of the year, they could double down on their youth movement and give the 24-year-old Black a chance to crack their Opening Day rotation. Black, who is ranked the club’s No. 9 prospect by MLB Pipeline, is considered close to big league-ready and gave up two runs on three hits over two innings in his Cactus League debut against the Angels on Monday.

Other rotation options include non-roster invitees Spencer Howard and Daulton Jefferies, both of whom have starting experience in the Majors. The Giants, of course, could also look outside the organization and pursue another free-agent starter such as Blake Snell, Jordan Montgomery or Michael Lorenzen.