MESA, Ariz. -- A's starter Jharel Cotton will seek a second opinion after receiving unfavorable news on his sore right elbow.
Cotton has been diagnosed with a sprained ulnar collateral ligament, which signifies a tear of the UCL. That's typically a precursor to Tommy John surgery, which would sideline Cotton, who also has a strained flexor muscle, for more than a year.
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The A's hold out hope that Cotton will be back in action sooner than that, but it's reasonable to assume he'll at least be out several months.
"We're looking for second opinions right now," A's manager Bob Melvin said, "so obviously not great news."
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Cotton, who was 9-10 with a 5.58 ERA in 24 starts during his 2017 rookie campaign, was considered a prime contender to rejoin Oakland's Opening Day rotation. His absence could strengthen Andrew Triggs' chances to grab one of the three open spots. The right-hander has been in consideration for either a rotation or bullpen job and will get a start Saturday against the host Giants in split-squad action.
Daniel Mengden and Paul Blackburn would likely fill out the rotation, which also includes Kendall Graveman and Sean Manaea. Daniel Gossett is also in consideration.
"Everybody else that would potentially be fighting for spots has had success before," Melvin said. "Predominately young and maybe not much of a track record, but we feel good about all of them."
There's an outside chance that the team's top prospect, lefty A.J. Puk, makes the cut. Puk started Thursday night's game against Seattle and gave up four runs on three hits with three walks in 2 2/3 innings. He has been the team's top pitching performer this spring but hasn't pitched above the Double-A level.
Cotton had a 3.75 ERA in four Cactus League outings, most recently firing four hitless innings against the Giants.
"We obviously don't know the amount of time that he's out," Melvin said, "but he was pitching really well, and toward the last inning of that game, it looked like the velo was dropping a little bit, so we tried to be proactive and get him out of there, but obviously some issues."
Other injury updates
A's outfielder Ramon Laureano -- the club's No. 22 prospect according to MLB Pipeline -- who was hit by a Roberto Gomez pitch during Monday's game against the Giants, was diagnosed with a fracture of the fifth metacarpal in his left hand. Laureano, who is expected to be out at least several weeks, was optioned to Triple-A Nashville, along with Jorge Mateo, following Tuesday's game.
Reliever Ryan Dull, meanwhile, threw his first bullpen session on Tuesday since being shut down with right shoulder soreness. Dull, who was slated for 20 pitches, is a "long shot at this point" to be ready for the regular season, Melvin said.
Lucroy in action
New A's catcher Jonathan Lucroy is tentatively scheduled to make his Cactus League debut in one of the club's split-squad games on Saturday.

Lucroy was sent to the Minor League side on Tuesday to catch reliever Emilio Pagan's two-inning appearance and to get several at-bats as Lucroy attempts to play catch-up.