The 2012 World Series MVP walked into the Giants' clubhouse at AT&T Park as if he had never left, shaking hands with players and grabbing bullpen catcher and former teammate Eli Whiteside in a bear hug from behind.
Sandoval, 30, served as the designated hitter for Class A San Jose later Saturday night, going 1-for-4 with an RBI single and walk. He will join Triple-A Sacramento on Tuesday where he will split time between third base and DH.
It was a scene few people thought possible after Sandoval left on bitter terms following the 2014 season after helping San Francisco to its third World Series title in five years.
Sandoval was apologetic upon his return, however, and blamed his comments then on immaturity.
"I apologize to the fans, especially for the things that I said -- both the things I said to [them and] my former teammates. There's a lot of things out there, man," Sandoval said.
Shortly after signing with the Boston Red Sox in 2014 on a three-year, $95 million free-agent contract, Sandoval said the Giants were disrespectful to him during their contract negotiations.
"I have to be respectful to the Giants organization. They give me the opportunity to be here. Now I get a second chance. I had a lot of special moments here. I have the greatest moments of my career here, so to have a second chance is the most important thing," Sandoval said.
The Red Sox released Sandoval on Wednesday when the third baseman didn't report after being designated for assignment last week. It officially ended the Boston tenure for the slugger, who never was healthy enough to live up to his big free-agent expectations.
Sandoval played in 126 games for Boston in 2015 and struggled with a .245 average and 10 home runs. He appeared in only three games last season due to injury and 32 games this season, hitting .212.
Sandoval added that he would have stayed in San Francisco if he could do it over again.
"[I was] emotional, a lot of things happened," Sandoval said. "I wish I could get back to that time to get the opportunity to sign again. I would sign it. But it's past. It's past. I'm moving forward right now to do the best."
Giants manager Bruce Bochy said Sandoval will have to prove himself in the minor leagues, both in the field and at the plate.
"It's a free look at a player who's done some good things in this game and has talent to hit a baseball," Bochy said. "Sometimes a change of scenery can get a player back to where he was, and he was pretty good here."
The Associated Press contributed to this report.