Bailey said he felt discomfort in the elbow after his past two spring training appearances.
"It's just a little discomfort," he said, according to MLB.com. "I felt something after my last outing [Sunday], so I figured I should have it checked out. I'll just be doing some therapy and give it some rest.
"Last year was probably the heaviest workload on my arm, so this is probably just from kicking it back up and my arm trying to get used to it again."
Bailey made 68 appearances in his rookie season, going 6-3 with a 1.84 ERA and 26 saves in 30 opportunities -- meaning he won or saved 32 of Oakland's games.
But Bailey says there's time to get his arm right before Opening Day.
"Better now than when the season starts. We have time to take care of it," Bailey said, according to the San Francisco Chronicle. "Last year was my first year of relieving. Getting up, getting down [in the bullpen], I wasn't used to that.
"This is probably a little side effect from that. But I'm very optimistic I'll be there for the start of the season."