Manager Bruce Bochy just said that Marco Scutaro was scratched from tonight’s game against the Rockies because of back stiffness. Bochy did not sound worried, saying it’s the typical back soreness that often runs through camp as players ramp up their activity. Prospect Ryan Cavan will start in Scutaro’s place. Also today, the Giants formalized what everyone knew was coming and reassigned middle-infield prospect Kensuke Tanaka to the minor-league camp. Tanaka struggled at the plate and, even worse, had an error-filled spring in the field. His attraction was his defense. In Wednesday’s game he grabbed a bouncer to his left about 40 feet away from Brandon Belt and heaved a throw so high and wide that Belt did not move a muscle to attempt a catch. “I will say this,” Bochy said. “He’s as hard a worker as you’ll see. We knew it was going to be an adjustment for him coming over here. We understand that. We tried him at third base and shortstop, so he had a lot on his plate. We don’t see him breaking with the club, so we’ll let him go down there and get his consistent at-bats in a more relaxed atmosphere.” The Giants also reassigned catchers Jackson Williams and Johnny Monell to the minors. These three cuts add much clarity to the roster situation. Wilson Valdez remains as the only healthy choice for the backup infield job, though the Giants are looking for a trade there.