To make room for Kotsay on the roster, the team optioned catcher Yasmani Grandal back to Triple-A Tucson after two games. He made his Major League debut on Saturday, going 0-for-1 after entering the game as a defensive replacement.
Kotsay has missed the past 20 games with a lower back strain, hit second in the lineup in the final game of a three-game series against the D-backs at Petco Park.
Kotsay missed the first 10 games of the season with a strained right calf.
"It's good to gets 'Kots' back," said Padres manager Bud Black. "He's done very well in the positions we have put him in as a pinch-hitter or getting some starts."
Kotsay is hitting .294 in his first 34 at-bats with the team with one home run and six RBIs.
"I've been making progress since before the team left town," Kotsay said, referring to the Padres' recent 10-game road trip. "I've been gauging the way I felt and right now I feel comfortable to go out there and play."
Kotsay's return comes eight days before the team plays another round of Interleague games on the road, three games in Seattle and then three more in Oakland. The team could potentially get Kotsay a start or two at designated hitter in those games to keep his bat in the lineup.
As for Grandal, he's itching to get back to San Diego, especially after having a taste, albeit a little one, of playing in the Major Leagues.
"It kind of gave me that little extra edge where I'm going back down to Triple-A and I want to get back up here," he said.