A’s hand Kendall Graveman the Opening Day ball

With staff ace Sonny Gray sidelined due to injury, Kendall Graveman will get the first Opening Day nod of his young career.

Until Thursday, when manager Bob Melvin made the announcement, the starting rotation had been the only area of the Oakland Athletics roster retaining any real debate. Now, while there are still three possible options for the final two spots on the staff, the top three slots have been given shape.

Melvin told Susan Slusser of the San Francisco Chronicle, discussions with Graveman regarding this decision began when Gray’s injury first occurred in early-March, and while he did show concern for his teammate, he was excited about the opportunity:

“He’s up for it. … He’s on a mission to be one of those guys who pitches at the top of the rotation for many years to come.”

Graveman, 26, stepped into the ace role in 2016 after Gray was placed on the disabled list following a fifth consecutive rough outing on May 20. Graveman proceeded to reel off a 9-2 record over the next three months, allowing 40 runs in 107 innings (3.36 ERA) over the stretch. In the midst of his 17-start run of success, he accounted for the only two Oakland complete games thrown all season.

Despite a stumble down the stretch, the sinker-baller finished his second full season in the major leagues with a respectable 10-11 record and 4.11 ERA.

For Graveman, success will be heavily dependent on command of that sinker, which he has gone to an nearly 60 percent of his pitches thrown in the majors, according to Fangraphs. He has, however, worked to improve his confidence in both the changeup and cutter, he told SFBay.

The first man to the mound for the green and gold, Graveman will look to get the 2017 campaign off on the right foot taking the ball against Mike Trout and the Los Angeles Angels of Anaheim at the Oakland Coliseum on April 3.

Between lefty Sean Manaea and righty Jharel Cotton, each 25, the A’s will fill the second and third spots in the rotation with a pair of wild-eyed youngsters taking part in their first big league Opening Day. The question remains, though: Who will fill which spot?

Manaea made his grand entrance into the big leagues via a late-April call-up, overcoming a struggle-ridden first month to finish his rookie season leading the A’s qualified starters in strikeouts (124) and ERA (3.86).

After making his major league debut in early-September, Cotton was nearly untouchable down the stretch, finishing the year with a 2-0 record and 2.15 ERA. That run of success came less than two months after he was acquired from the Los Angeles Dodgers in a trade that involved a total of five players, including fan favorite Josh Reddick and Rich Hill heading south.

Despite the A’s getting a trio of high-level pitching prospects in return, it was Cotton who Vice President of Baseball Operations Billy Beane fought for, he said speaking with Bay Area media March 17:

“He was the last guy we were trying to get in the deal; when me and (Dodgers GM) Farhan (Zaidi) were doing that deal, that was the sticking point. … We knew he was good, but he’s been very, very good since he came over, and his work in the big leagues at the end of the year was unbelievable.”

Beane joked that he was the only member of the A’s front office to hold Cotton in such high regard.

Both young hurlers have an affinity for giving up the long ball — Manaea having allowed 20 in 144-2/3 innings and Cotton four in 29-1/3. That is an issue which must be focused on in search of immediate growth.

Things get a bit more hairy when it comes to the final two spots in the Oakland rotation. With 10 days left before Opening Night, competition remains between Raul Alcantara, Jesse Hahn and Andrew Triggs for those final two spots.

Of the former bullpenner who had made just one professional start prior to 2016, Beane said that the seamless transition into starting has been impressive:

“He did a great job when he stepped in as a starter last year, and was one of the pleasant surprises (of the season). … If he can throw like he did last year, that’s quite a find.”

Going 1-1 with a 2.70 ERA in seven starts down the stretch a year ago gave Triggs a leg up on the competition heading into spring, and he has done nothing to relinquish that advantage.

As far as the No. 5 spot, Hahn’s spring performance may not have been enough to surmount Alcantara’s lack of minor league options.

Denying Alcantara a roster spot would make him available to other teams through a waiver claim. But that hasn’t been the only factor. Hahn has just not done enough to warrant Alcantara’s waiver fate — the veteran righty has allowed the opposition a robust .327 leading to an unacceptable 1.67 WHIP.

That may not be a huge upgrade over the his challenger (.259, 1.36), but the chips had been stacked against him from the beginning, and Triggs, the man Hahn may have had in his crosshairs, allotted the 27 year-old no help posting a .242 opponent’s average and 1.06 WHIP.

While there is still time to seize the day, Hahn appears ticketed for another flight to Nashville where a spot with the Triple-A Sounds will be waiting, leaving the Oakland with its regular season starting rotation.

Kalama Hines is SFBay’s Oakland Athletics beat writer. Follow @SFBay and @HineSight_2020 on Twitter and at SFBay.ca for full coverage of A’s baseball.