Athletics place pitcher Alex Wood on IL with rotator cuff tendonitis

And then there were two.

The Athletics placed Opening Day starter Alex Wood on the 15-day injured list Wednesday with rotator cuff tendonitis, where the veteran left-hander will join Paul Blackburn (metatarsal stress reaction) and Joe Boyle (lower back strain).

Wood pitched a season low two innings in an 8-4 loss in Seattle Sunday, with both  manager Mark Kotsay and Wood conceding there was an issue with his shoulder. Wood returned home for a doctor’s visit and an MRI.

It’s not known how much time Wood is expected to miss. Kotsay is scheduled to speak to the media before the A’s face the Houston Astros at Minute Maid Park in the third game of a four-game series.

The A’s also signed right-handed pitcher Aaron Brooks off the Las Vegas roster and promoted left-hander Hogan Harris for the second time this season. Brooks is the scheduled starter Wednesday night against Houston.

Brady Basso, a left-hander called up from Double-A Midland on Tuesday as a “just in case” long relief option, has been shipped back to Triple-A Las Vegas. In addition, shortstop Darell Hernaiz (ankle) was transferred to the 60-day injured list.

Brooks will become just the third pitcher outside of the original rotation to start for the A’s, joining Joey Estes and Osvaldo Bido. With Wood joining Blackburn and Boyle on the sidelines, the only two starters to stay on schedule have been J.P. Sears and Ross Stripling.

Wood, 33, has struggled to regain his form after being in an unfamiliar role of a sometimes starter and sometimes reliever under Gabe Kapler with the Giants last season. He pitched five innings or more just four times in nine starts with an earned run average of 5.26.