Making his second Cactus League start, Cain struck out seven, fanning at least one in each inning. He also coaxed four ground balls and four popups or flyouts. Olt came closest to collecting a hit off Cain, sending a second-inning line drive to shallow center field that Gregor Blanco caught.
"I threw good pitches when I was ahead on the count, which is always nice," Cain said. "At times you feel like you get in good counts and you're not able to finish guys, but today we were able to do that."
"It's exciting to see a guy out there competing like Cain does," Cubs starter Jeff Samardzija said. "He's that type of guy who comes out and takes the ball every fifth day and I guarantee you every time he takes the ball, his manager has a good feeling they'll win that game."
Samardzija struck out four in three innings before lapsing. Michael Morse singled to lead off the fourth inning and Hunter Pence doubled one out later. Both rushed home as Pablo Sandoval grounded a 1-1 pitch past shortstop.
"They're a great team to work against, a former world championship team," Samardzija said. "They come with a plan, a lot of smart players who have played together for a long time. You really get tested on days like this. I thought it went excellent. I gave up a couple runs, and singles that score runs, you can live with that."
Chicago halved the difference in the sixth inning against left-hander David Huff, who made his Cactus League debut after enduring shoulder problems. Roberts delivered a leadoff single, moved to second base on a wild pitch and scored on Emilio Bonifacio's two-out single.
Up next: If catcher Buster Posey returns to the lineup Tuesday, which is quite possible since he sat out Monday, he'll collaborate with Tim Hudson for the third Cactus League start in a row, giving the batterymates increased familiarity with each other as the regular season approaches. Though Hudson's known for coaxing ground balls, he has struck out four batters in five innings spanning his previous two starts. The Giants will be looking for their first hit off Reds starter Tony Cingrani. San Francisco mustered three walks and nothing else off the left-hander in three innings last Thursday.
Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.