This gave the embattled Giants, saddled with the Major Leagues' worst record after losing five consecutive games, a moment to savor. Arroyo's bases-clearing gapper prompted an outbreak of emotional fist-pumping that reflected the team's cathartic joy.
"That was a lot of frustration from the past week coming out," Arroyo said.
The Giants would have welcomed this kind of contribution from anyone. For Arroyo to deliver in this situation bolstered their belief that the prized 21-year-old will continue to generate such highlights.
"It's great to see the aggressiveness that he's had," said right-hander Matt Cain, another Giant who provided thrills at a similar age. "He's learning a ton, and it's fun to watch that because you can see him grasp things really quickly. He's learning on the fly. It's going to be fun to watch him throughout the years."
Outfielder Justin Ruggiano, a recent Giants callup, watched Arroyo hit .446 for Triple-A Sacramento before San Francisco summoned him on April 24. "He was Ted Williams down there," Ruggiano said. "I was telling him to drive to San Fran after games, because he'd get two or three hits a night. For such a young kid, he has such a good approach. I don't think any situation's too big for him."
That was evident one day before Arroyo's game-winning hit and one day after he struck out four times in four plate appearances in Monday's 4-3 loss to the Mets.
"Obviously, nobody wants to punch out four times in a game," Arroyo told an MLB.com reporter almost cheerfully on Tuesday. "But I think that's part of developing and part of just being a ballplayer. I think that was a good game for me to have early on, so I understand these guys are going to find what they think your weaknesses are and try to attack them."
Giants manager Bruce Bochy will do all he can to further Arroyo's education.
"They're pitching him tough. We're staying with him, trust me," Bochy said. "This kid's a tough kid. He's the one guy I don't worry about [bad experiences] having a lingering effect."
Arroyo therefore was composed when he confronted the formidable but plainly unraveling Familia with one out in the ninth, a run in and the score tied at 3.
"I saw he was a little wild today. But he still has that good stuff," Arroyo said. "He can get you to swing at a pitch you don't necessarily want to swing at."
Arroyo swung at a 1-0 fastball measured at 95 mph, and he rocketed it into left-center field.
"I knew I barrelled it pretty well," Arroyo said. "It was nice to put a swing on a ball and be in control of that at-bat."
Chris Haft has covered the Giants since 2005, and for MLB.com since 2007. Follow him on Twitter at @sfgiantsbeat and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.