The right-hander allowed one run on one hit while striking out three without a walk in two innings.
Coming into the game in the seventh inning, Foulke allowed a single before eventually allowing the runner to score on a balk.
Manager Bob Geren appeared hopeful about Foulke, who is sitting on the 15-day disabled list since April 11 with neck stiffness.
"I saw most of his performance on the computer," Geren said before the opener of a three-game series against Baltimore. "He's still scheduled to be available for us on Wednesday."
Foulke, who signed a one-year deal with the A's just before the opening of Spring Training, recorded a save against the Toronto Blue Jays on April 10, but his sore neck has kept him off the active roster.
Foulke was not the only Oakland player in Sacramento on a rehab assignment Monday. Travis Buck, on the 15-day DL with shin splints that started bothering him during Spring Training, played center field, led off and went 1-for-3 with two walks. Geren said the outfielder is still expected to make the team's nine-game road trip starting Thursday.
Jane Lee is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.