MESA, Ariz. — Like every other pitcher in the Oakland Athletics' deep bullpen, Liam Hendriks is expecting to pitch a lot this season.

The tricky question for manager Bob Melvin going into spring training: Who gets to go first?

The Athletics rotation is a major uncertainty heading into camp, with the first workout for pitchers and catchers set for Monday. Of course, that's nothing new for Melvin. Oakland's rotation was wrecked by injuries last season, prompting the A's to lean on their relief pitchers as "openers" to start games. With at least three spots in the rotation currently wide open, Oakland might again be forced to get creative with the early innings.

Hendriks became the most dependable in that role last season, making nine of the 10 "opener" starts for Oakland in September and October, including in the AL wild-card game against the Yankees.

The makeshift bullpen games helped the A's earn a surprising post-season appearance, and Hendriks is eager to return to the role. He's ready to pitch every other day if asked — "I'd love to be able to get to 81 games pitched, just to be able to say I did it," he said.

Melvin smiled at that suggestion, but he hopes Oakland's staff won't have to be quite so untraditional.

"We're open to just about anything," Melvin said. "But I don't know if we're fixated on going into spring right away saying, 'We're going to start with an opener on this game.' I haven't scheduled it out that way."

The Athletics are getting an early start on spring training because they're heading to Japan for a season-opening series on March 20-21. The teams will be allowed expanded 28-man rosters for those games, and Melvin expects to use the extra roster space to more carefully manage his pitchers.

"That will allow us to do things at our pace," Melvin said. "It's more about the pitching than anything else and making sure they're ready. With some extra guys, it means we don't have to push guys to try to get somebody ready to throw 100 pitches in this game (in Tokyo). I don't know if that's realistic."

Besides Mike Fiers and newcomer Marco Estrada, nothing is set in the rotation. Estrada battled hip and back problems last season while with the Blue Jays, yet still made 28 starts, posting a 7-14 record and 5.64 ERA.

"I have to be a little smarter about things like that. If I'm in that much pain, I should probably take it easy," Estrada said. "I like making all my starts. My goal is to try to make at least 30 starts. That's something I want to do for these guys, I want to give them innings."

Last season, Oakland starters combined for 824 1/3 innings, the fewest in team history. Every member of the season-opening starting rotation dealt with injuries.

Daniel Mengden is the most likely pitcher to join Fiers and Estrada in the rotation. He appeared in 22 games (17 starts) last season and was often used as the long man following the "openers." Frankie Montas and Chris Bassitt are also strong possibilities, while injured starters Jharel Cotton, Sean Manaea and Andrew Triggs may return at some point in 2019.

NOTES: The A's still don't know when or if top draft pick Kyler Murray will report to camp. The two-sport star has a locker and a No. 73 jersey waiting for him in Oakland's clubhouse at Hohokam Park, but general manager David Forst said Sunday they were still talking to the Murray family as the Heisman Trophy winner tries to decide which sport to pursue.

Third baseman Matt Chapman, who had thumb surgery in October and a distal clavicle resection procedure in December on his non-throwing shoulder, is not expected to be ready for the first Cactus League game but said he was making good progress.

Right-hander James Kaprielian has had a setback in his recovery from shoulder issues, Melvin said. Kaprielian will have an MRI and is not expected to start training camp with the rest of the team's pitchers. The 24-year-old was acquired from the Yankees for Sonny Gray in 2017 but hasn't pitched in a game since 2016.

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