MESA, Ariz. -- Yet another A's starter is injured, and it has taken the guesswork out of their Opening Day rotation.
Right-hander Paul Blackburn has been diagnosed with a forearm strain and is considered day to day after an MRI revealed no structural damage, an unfortunate development that leaves just five healthy A's starters in camp.
By default, that means the season-opening rotation will include Kendall Graveman, Sean Manaea, Daniel Mengden, Andrew Triggs and Daniel Gossett, though not necessarily in that order.
Blackburn, though disappointed, is mostly relieved; a forearm strain is often a precursor to a torn ulnar collateral ligament, which requires Tommy John surgery. On Wednesday, fellow starter Jharel Cotton underwent the procedure, precluding him from pitching this year.
Blackburn will be shut down for at least 10 days.
"You prepare all offseason to start the year healthy, and unfortunately that's not the case for me," Blackburn said. "There's nothing you can do about it. I'm not going to sit here feeling sorry for myself or expect anyone else to feel sorry for me, I'm just going to train and prepare to get back as soon as I can."
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Blackburn and Cotton were expected to be key contributors to a rotation that was already of great concern for the A's, who signed Trevor Cahill to a one-year deal in the wake of Cotton's injury. Despite pitching in Thursday's game vs. the Rockies, Cahill won't be ready to start when the season opens, A's manager Bob Melvin confirmed.
The A's also inked Brett Anderson to a Minor League deal but won't have him readily available to start soon, either.
"We were a little short on depth," Melvin said. "Certainly that's why we went out and got a couple pitchers, but it's starting to get fairly significant right now, so hopefully there is not anything that is going to be too long for [Blackburn] there. But at this point in time, it's going to be a long shot for him to start the season."
Blackburn looked out of whack in his last start against the Dodgers, allowing seven runs in 3 1/3 innings. He had yielded just two runs in his previous 10 innings.
"It wasn't like anything kind of popped up that was scary to me or anything like that, it was just sore, and we'll take it day by day and kind of go from there," Blackburn said. "I didn't think it was anything major, it just really felt sore."
Blackburn was the A's top pitching performer following his midseason promotion in 2017 before a deep bone bruise in his pitching hand prematurely ended his rookie season on Aug. 22. He completed at least six innings in six of his first seven starts and compiled a 3.22 ERA in 10 starts overall.