He singled and scored when the Padres jumped out to a lead in the third. He later squeezed in the go-ahead run, with a perfect squeeze bunt in the seventh.
"That was great execution on his part," said manager Andy Green. "That's not the easiest thing in the world to do -- bunt a curveball that's down. He got a great bunt down there."
But Amarista's most important contribution may have been a subconscious act during a controversial ruling in the sixth. Third-base umpire Will Little had called the infield fly rule on a Darin Ruf popup into shallow left field. Shortstop Alexei Ramirez couldn't make the catch and threw to third.
Amarista stepped on the bag, thinking he had recorded an out -- but with the infield fly rule in effect, his touching the base was rendered moot. Still, Amarista subconsciously tagged the runner, Odubel Herrera, anyway -- and that tag proved to be the reason Herrera was eventually ruled out on replay.
"When the ball bounced, I realized that the runner was coming, and I tagged him," Amarista said, through a translator.
But why tag him if he thought he had already recorded an out?
"Un instinto," Amarista said.
That instinct may have been the difference in the game.
Amarista did not make the Opening Day roster, but was recalled Sunday after Yangervis Solarte was placed on the disabled list. It didn't take long for him to make his presence felt.
"He was great, comes up first at-bat -- we weren't doing too much offensively -- and he lines a single to get a rally going, and eventually scores a run," Green said. "... He was in the game today. He was very active. That bunt won the game for us. I don't think there's another way to look at it."
AJ Cassavell is a reporter for MLB.com. Follow him on Twitter @ajcassavell. This story was not subject to the approval of Major League Baseball or its clubs.