How worried should the Giants be about injuries to Matt Cain and Jake Peavy?

While the Giants did well to hold off the Diamondbacks in their series opener on Monday night, the team’s latest injury report tempered the optimism that followed a hard fought 5-4 win in the desert.

Hours before first pitch, news broke that Matt Cain underwent an MRI for forearm tightness, effectively sidelining him for his scheduled Wednesday start, per Chris Haft of MLB.com. To make matters worse, Jake Peavy was also scratched from Game 2 of the series with stiffness in his back, with the hope that he’ll be ready for one of the team’s weekend games in San Diego.

Losing two of the rotation’s top arms obviously stings, but how worried should the Giants really be? Well, given the nature of the injuries and the players’ past histories, there are some legitimate concerns to mull over.

But first: The good. Hours after the game, it was revealed that Cain’s injury was actually just a strained tendon:

Forearm tightness is often the harbinger of Tommy John surgery, so Giants fans should take a collective sigh of relief even though Cain is bound for the disabled list. The silver lining for Peavy is similar: he’s only out for the short-term, with his current prognosis costing him just a single start. If both come back when they’re supposed to, the Giants can bridge the gap without much issue. Ryan Vogelsong, who’s more adept at starting than he is long relief, is already slated to take Peavy’s turn in the rotation, while Tim Lincecum can move up a game to fill Cain’s spot. If not Lincecum, Chris Heston, who had an eye-opening spring (15 IP, 2.40 ERA, 10 K), might get a well-deserved call-up:

Even Yusmeiro Petit, despite Bruce Bochy’s preference to keep him in long relief, could be used in a pinch.

The bad news is, the Giants don’t just have to worry about Peavy and Cain coming back in short order—the bigger question is if both can stay healthy and perform. Neither was close to 100 percent in spring, and their numbers showed it. Peavy in particular was knocked around in all of his starts, finishing with more earned runs (20) than innings pitched (18.1).

Some struggles had to be expected given his age and the fact that he topped 200 innings last season—a feat he’s achieved just twice in the past seven years—but pairing dead arm with a back flare-up doesn’t instill confidence that he can come close to replicating the brilliant second half he enjoyed in 2014.

Don’t forget: Last season was, for a time, rumored to be Peavy’s last given an extensive injury history that includes work on his shoulder and elbow. Even if the former flamethrower can avoid a DL stint, there is always the fear that the soon-to-be 34-year-old resumes the career decline he experienced before his resurgence in San Francisco.

Cain, despite being out for a week longer than his rotation-mate, is in a better position to bounce back. Excluding last year, when he went under the knife to remove bone chips from his throwing arm, Cain has been an absolute workhorse, averaging over 200 innings pitched across his eight full seasons in the bigs. Also encouraging is that the three-time All-Star claimed that his recent stiffness felt different than the soreness he experienced in the spring, which doctors had mentioned as a possibility following his elbow surgery, per Andrew Baggarly of the Mercury News.

Still, the Giants would be wise to exercise caution in bringing Cain back up to speed, as the need for a reliable No. 2 behind Madison Bumgarner has never been more apparent following his record-setting workload last postseason.

All things considered, if both Cain and Peavy are able to remain on their current timetables, and if both can show off the form that Giants faithful have grown accustomed to seeing, the team will be more than fine. Realistically, though, I would lower expectations to mixed results for Peavy—in terms of both health and production—and a gradual return to form for Cain.

Regardless of what happens, the Giants can thank their lucky stars that they have reasonable pitching depth, thanks in part to a strange parting of ways between the Astros and Vogelsong, which led to San Francisco swooping him up on the cheap. After all, spring woes aside, the veteran has a new weapon in his arsenal: