SCOTTSDALE, Ariz.–The Giants nearly broke spring camp without suffering any serious losses due to injury.

But Thursday evening, manager Bruce Bochy revealed that starter Jeff Samardzija was diagnosed with as trained pectoral muscle after undergoing an MRI.

The Giants are concerned with Samardzija’s shoulder after the team’s No. 3 starter has struggled for much of spring training.

“He’ll go a week without throwing the ball and then crank it back up,” Bochy said. “It shouldn’t take long to get him back on the mound so it’s good news.”

In a Minor League outing on Wednesday, Samardzija threw three scoreless innings before allowing a pair of home runs and a double in the fourth. It marked Samardzija’s third straight start in which he’s surrendered at least two home runs in the same inning. Related Articles When Giants need him at his best, Johnny Cueto struggles in blowout loss to Rockies

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Bochy said there’s a “high chance” Samardzija will start the season on the disabled list and indicated non-roster invitee Derek Holland is the top candidate to replace Samardzija in the rotation.

Samardzija exited his Wednesday outing abruptly after 73 pitches, creating a long delay in between innings as the Giants’ Triple-A spring club needed additional time to prepare a pitcher to get loose. Samardzija didn’t indicate he was feeling pain, but Bochy thinks it’s possible the right-hander has dealt with the issue for much of the spring.

“He’s such a tough guy and a strong man that he just kept pitching with it,” Bochy said. “I’ll know more here pretty soon.”

Bochy said Wednesday evening that Samardzija dealt with a small neck injury earlier this spring, but that his neck did not appear to bother him recently.

The Giants were inching toward announcing their starting rotation, but Samardzija’s injury will temporarily prevent San Francisco from doing so. To move forward, the Giants will evaluate the various internal options at their disposal and consider how they want to structure their initial Opening Day roster.

Samardzija is one of the most durable pitchers in all of baseball, logging at least 200 innings in each of the last five seasons. The Giants lost two of their top arms, Madison Bumgarner and Johnny Cueto, to injuries last season, and don’t have much rotational depth within their organization.

General manager Bobby Evans and Brian Sabean prioritized building depth in the bullpen and in the lineup with their offseason acquisitions, but the Giants’ management didn’t move aggressively to add another arm to its rotation. At this point in the spring, there are still a few veteran starters like John Lackey, R.A. Dickey and Scott Feldman available, but the club wouldn’t have enough time to prepare a free agent arm to join a rotation before the end of April.

With the regular season now one week away, the Giants are considering keeping 13 pitchers and 12 position players on their Opening Day roster. On Friday, Bochy plans to start Buster Posey at first base and Brandon Belt in left field, as the Giants are now considering keeping just four outfielders instead of five.

Thanks to the reemergence of Pablo Sandoval this spring, the Giants could use Belt as an extra outfielder when Hunter Pence needs a rest in left field and have either Sandoval or Posey play first.

The Giants currently have 14 pitchers in Major League camp, including Samardzija and left-handed reliever Will Smith. Smith will start the season on the disabled list as he continues recovering from Tommy John surgery, and with Samardzija set to do the same, Rule-5 Draft choice Julian Fernandez could begin the year in the Giants’ bullpen.

Should the Giants lose Samardzija for the start of the regular season, they would likely begin the year relying on Bumgarner, Cueto, Holland, Chris Stratton and Ty Blach in the starting rotation. However, early off days do afford the Giants the luxury of starting the year with a four-man rotation in the event Samardzija’s injury will only keep him out a short period of time.

Because off days follow the Giants’ first road series in Los Angeles and their first home series against the Mariners, the club doesn’t technically need a fifth starter until April 12 when the team travels to San Diego.

Stratton and Blach have combined for fewer than 250.0 career innings, while Holland hasn’t thrown more than 135.0 innings in a season since 2013. Though the Giants anticipate Stratton and Blach will have the durability to remain in their starting rotation for a full season, Holland posted a 6.20 ERA in 135.0 innings with the Chicago White Sox before being released in September of last year.

With questions and uncertainty now confronting his starting rotation, Bochy said a bullpen that appears much improved could shoulder more of the load this season.

“They should help out so we have help for these starters,” Bochy said. “We’re not going to cut them short because of our bullpen, but we want to keep them fresh. the fact that we have some good arms out there is going to make them better.”