Angel Pagan, Miguel Olivo and Conor Gillaspie each added two hits for the Giants, who have lost 16 of the past 20 spring games to the A's. They play three more times in the Bay Bridge Series.
Chris Coghlan and Matt Chapman each hit a two-run homer off Samardzija. It was the fourth home run of the spring for Chapman.
"I keep telling myself he's not on the roster yet," Bassitt said. "But he's unbelievable. His defense is there, his offense is there, his arm is a cannon. ... He's forcing the issue."
Bassitt was hit in the left hamstring by Olivo's line drive in the first but said it did not interfere with his outing.
Athletics: Bassitt rebounded from a rough minor league start the previous time out and put together a good effort.
"It couldn't get any worse than the last time," Bassitt said. "I feel like I'm way ahead of what I used to be and am just tweaking stuff."
As for getting hit by the first-inning line drive?
"When it's hit that hard, you definitely feel it," he said. "But it never cramped up. It's still a little sore."
Giants: Samardzija called his fifth start a great day despite allowing six runs and six hits. He struck out three and did not walk a batter.
"It's spring training, man. I feel good," he said. "When you look at it as a whole, it's exactly what we wanted. I left a couple over the plate and they took advantage. I wanted to make sure I got through five and I felt good so I went out for the sixth."
Samardzija said his splitter was the best it's been all spring.
"It was great," he said. "I've been fishing for it the last few times out. I got a couple of swing-and-misses."
Athletics: LHP Sean Doolittle was scheduled for a long toss and bullpen session. A's manager Bob Melvin said Doolittle would likely throw in a minor league game before pitching in a spring game. "That will give him a chance to work on things," Melvin said. ... OF Sam Fuld has a moderate shoulder strain and will miss at least three weeks.
Giants: C Trevor Brown was removed from the game following the top of the first inning with a bruised left forearm. "It looked like a back swing," Samardzija said. "I hope he's OK."
Giants: A pair of split-squad games on Tuesday. RHP Jake Peavy pitches in the afternoon against the White Sox in Glendale. RHP Mat Latos goes for Chicago. At night, LHP Ty Blach starts against the host Arizona Diamondbacks and RHP Rubby De La Rosa.