"I don't think I've ever been that excited to take live BP, ever," Posey said. "It was fun."
Cain allowed only one hard-hit ball during his pitching stint: Hector Sanchez's line drive that struck Cain's left calf. Cain tumbled head over heels but threw a few more pitches and completed his round on the mound.
Sandoval also went down in a heap when left-hander Jeremy Affeldt's fastball hit him in the ribs, slightly beneath his left armpit. The unflappable Sandoval finished the rest of the workout without further incident.
By escaping injury, Cain and Sandoval provided indications that this is indeed a new year. San Francisco used the disabled list a Major League-high 25 times in 2011.
The unluckiest Giant was Posey, who was hurt in a May 25 home-plate collision with Florida's Scott Cousins. On Sunday, Posey donned his catcher's gear to receive Cain's BP pitches. This represented another first for Posey, who hadn't squatted behind the plate with anybody batting since his fateful encounter with Cousins.
But Posey's hitting captured more attention. After mustering a foul fly to right and a comebacker in his first trip to the batting cage against Romo, the 2010 National League Rookie of the Year demonstrated that he still possesses the aptitude to hit to all fields.
"Right now this is all about trying to get your timing right and see some pitches," Posey said. "I guess I didn't really know what to expect. But I was happy with the way I felt."
Manager Bruce Bochy said that he'll decide in two or three days whether Posey will participate in Saturday's exhibition opener against Arizona. If Romo had a vote, he'd put Posey in the lineup.
"Right out of the gate, he was swinging," Romo said. "It was very uplifting to see that. Seeing him out there puts us through the roof."
Cain headed in a different direction when Sanchez's liner smacked into him. But Cain, tended to by head athletic trainer Dave Groeschner, rose quickly and tested himself with a warmup throw before continuing to pitch.
Though Cain threw without a protective L-screen, he's unlikely to use it the next time he throws BP.
"I just don't like the L-screen," Cain said. "I feel like you have to throw around it and it's just an uncomfortable feeling for me to throw with it."
Though the Giants dodged the misfortune of losing a top starting pitcher to a preventable injury, Bochy agreed with Cain.
"Sometimes [the screen] can affect their delivery," Bochy said. "That's fine with me, because you have to learn to field your position and defend yourself. Sometimes you get bad habits using that screen. You drop your guard, and you can't do that during a game."
Sandoval was extremely alert as he awaited Affeldt's final delivery before a couple of practice pitchouts. But the switch-hitting third baseman, batting right-handed against Affeldt, had no chance to avoid the ball.
"I was hoping he'd get out of the way. I knew when I threw it that it was way too far in," said Affeldt, who explained that trying a new slide-step motion may have robbed him of control. "I saw it go right at him out of my hand. That's how I knew it was bad. But he's a hitter that doesn't move. That's why he's such a good hitter. He's going to hold in there as long as possible."
Sandoval grinned widely as he insisted that he was unharmed.
"Nothing serious," he said. "It happens."