Manager Bud Black said it was good to see Alonso in the lineup. He singled in his first at-bat.
"He's a rookie player trying to establish himself in this league," Black said. "He wants to be out there. He wants to play. This guy has been a guy who plays every day."
Alonso made his 66th start of the season on Wednesday in the Padres' 76th game. He pinch-hit in Tuesday's game, striking out in his only at-bat in the ninth inning.
Entering Wednesday, Alonso was batting .253 with two homers and 18 RBIs. After a solid May, he struggled a little in his first 21 games in June, hitting .181 with 15 strikeouts and three walks.