"We have some versatile guys, and who knows how long it's for, but we really did need an arm," A's manager Bob Melvin said. "We were under the gun yesterday, and we're going to be under the gun again [Tuesday].
"Triggs was basically our length, and not having him and him not responding to the point where we feel comfortable using him in the next couple of days, we made the move for Daniel."
Triggs was rushed into relief duties in the first inning of Sunday's loss to the Blue Jays when starter Rich Hill aggravated a blister, but he, too, was shortly out of the game after taking a line drive to his shin. There's still no timetable for when Hill will make his next start, though Melvin said he's not yet a DL candidate.
"Probably a little bit more careful with it right now," Melvin said, "but it's probably going to be a few days before we have any inclination of when he's going to play catch and then potentially start again."
Coulombe, 26, joins the A's for the fifth time this season, having posted a 4.50 ERA in 13 relief appearances. He's been tremendous for the Sounds, pitching to a 1.08 ERA in 20 outings.
• Catcher Josh Phegley, who underwent right knee surgery earlier this month to remove a cruciate ligament cyst, began a series of baseball activities Tuesday, taking a handful of swings and playing catch. It's not yet known when he will begin a Minor League rehab assignment.
Jane Lee has covered the A's for MLB.com since 2010. Follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.