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3/26/2014 8:27 P.M. ET

Cain's final tuneup is a clunker

SCOTTSDALE, Ariz. -- Matt Cain was relatively unconcerned with his subpar pitching line Wednesday against the Colorado Rockies, which sealed his spring ERA at 7.47.

"My arm strength, even today, was fine," said Cain, who surrendered six runs and nine hits in five innings. "It's just a matter of making pitches. I know it's going to be there."

Cain began his Cactus League campaign with eight one-hit innings spanning two appearances, then yielded 13 runs in 7 2/3 innings in his final two exhibition outings.

Scutaro to begin the season on disabled list

SCOTTSDALE, Ariz. -- Though Marco Scutaro didn't admit it directly, he acknowledged Wednesday that he's bound for the 15-day disabled list as he strives to overcome back trouble.

Scutaro, who appeared in just one Cactus League exhibition, said that he will remain in Arizona to work out, perform light baseball-related activities and continue efforts to ease his discomfort. Once Scutaro is officially placed on the disabled list, the start of his DL assignment could be rewound 10 days retroactively, making him eligible for activation as early as April 4.

Whether Scutaro can work himself into playing shape by then is debatable.

"I've been very consistent, feeling pretty much the same. Not too bad, not too good," he said. "At the same time, I'm not playing nine innings every day."

Manager Bruce Bochy said that Scutaro will undergo more diagnostic tests Thursday.

"It's hard to have a timetable [for Scutaro's recovery] because we can't get this thing figured out," Bochy said. "That's why we're going to have more tests tomorrow."

Scutaro's unavailability meant that a pair of reserve infielders who began spring on the proverbial bubble, non-roster invitee Brandon Hicks and rookie Ehire Adrianza, will make the Opening Day roster.

Scutaro received an epidural shot last Thursday in a futile attempt to treat his back. "The shot didn't work," the 38-year-old said. "It worked for a day and a half."

That prompted the diagnostic nerve block that Scutaro received Tuesday. Had Scutaro's pain subsided, doctors could have performed another procedure, involving the deadening of a nerve, that might have provided relief. "In my case, it didn't go away," Scutaro said.

Scutaro said that he received a cortisone shot in a lower area of his back in the continuing search for a source of relief.

Knee injury to land Affeldt on 15-day disabled list

SCOTTSDALE, Ariz. -- Giants left-hander Jeremy Affeldt will begin the season on the 15-day disabled list with a sprained medial collateral ligament in his right knee.

Manager Bruce Bochy said that Affeldt felt discomfort in the knee when he pitched against the Chicago White Sox last Saturday, when he yielded four runs in one-third of an inning. Bochy said that Affeldt wasn't using the knee brace he typically wears.

Because Bochy indicated that both long-relief candidates, Yusmeiro Petit and David Huff, would make the Opening Night roster, Affeldt's injury left Derek Law, Jean Machi and Juan Gutierrez competing for the remaining two spots in the bullpen.

Giants bring five extra players home for A's series

SCOTTSDALE, Ariz. -- Dipping into Minor League camp, the Giants took three additional pitchers and two more position players back home with them to provide roster reinforcements for the three-game Bay Bridge Series against the Oakland A's.

Right-handers Erik Cordier and Heath Hembree, left-hander Dan Runzler, catcher Guillermo Quiroz and infielder Chris Dominguez joined the contingent that will face Oakland Thursday through Saturday.

Hembree and Quiroz spent part of last year with the Giants. Runzler appeared in 89 games for San Francisco from 2009-12.

Posey sits out Cactus League finale as a precaution

SCOTTSDALE, Ariz. -- The Giants exercised caution by scratching catcher Buster Posey from Wednesday's lineup against the Colorado Rockies with tightness in his left hamstring.

Giants manager Bruce Bochy said that Posey could have played and will indeed return to the lineup Thursday against Oakland.

Posey thrived in his 16 Cactus League games, batting .419 (18-for-43) with two home runs and 12 RBIs.

Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.