"It's nice when you know in the bullpen that you have your stuff and you're not having to force everything," said Samardzija, who attributed his clean innings to his slider.
Aside from yielding Brandon Crawford's second-inning homer, A's right-hander Jharel Cotton looked effective, allowing five hits in four innings. Oakland's projected No. 3 starter walked one and struck out two.
"This Spring Training was good," Cotton said. "Now time for the real stuff to start."
The Giants maintained that slender lead until the eighth inning, when Jaff Decker's two-out double off Hunter Strickland scored Mark Canha and drew the A's even.