The strength of the A’s is their pitching staff. And the strength of the A’s pitching staff — at least as far as the future is concerned — is Jarrod Parker. The 23-year-old right-hander is considered an ace-in-the-making, which is why Oakland was willing to trade Trevor Cahill and Craig Breslow to acquire him from Arizona this past December. Now 30 months removed from Tommy John surgery, Parker began this season in Triple-A before making his first Oakland start last Wednesday. If all goes as planned, he’ll be making plenty more in years to come.

Parker talked about his enhanced repertoire — which includes a two-seamer and a pair of changeups — prior to last night’s game at Fenway Park.

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Parker on his repertoire and approach: “I throw four- and two-seamers, a changeup, a slider and a curveball. I’m aggressive. I like to attack the zone, down. I started throwing a two-seamer last year and it has helped me to use fewer pitches and go deeper into games. After surgery, I also really focused on learning a good changeup. I’m trying to not throw as many breaking balls, just use them when I need to.

“I work down more than I did [before the surgery]. The two seamer really helps me get down in front, because when it’s up, it’s not doing anything. It helps remind me to get down through it and finish out in front. I think that takes a lot of stress off of my elbow.”

On changing eye levels: “[Working up in the zone] is something I know I need to do. Early on, I want to establish the fastball down and be as aggressive as I can, but in certain counts I’ll want to raise the hitter’s eye level, then come back with a curveball.

“Less damage can be done when the ball is down. For me, ground balls are better than fly balls. That’s something I really push for, because down in the zone with some movement is going to be a little harder to hit. But changing eye levels by going up in the zone is important. It’s tough for a hitter to lock in when you’re moving the ball up and down.”

On his changeups: “Something I’ve taken pride in is being able to command the changeup. I’ve been trying to be as efficient as I can and my changeup has been kind of an equalizer for me. It has the same spin as my fastball, I hope.

“I throw more of a split-change, but sometimes I throw a circle change. I try to throw a few different ones. If I’m throwing a four-seam fastball, I’m going to throw a four-seam changeup. Or if I’m throwing a two-seam fastball, it’s going to be a two-seam changeup. I want it to look the same out of my hand.

“[Throwing two different changeups] is maybe kind of unique, but it’s something other guys are probably working on, too. I can go into an outing with a game plan. I can throw one for a strike and hopefully put away a guy with the other.”

On his first Oakland start: “In my last start, I followed Zuk [Kurt Suzuki], which made it easy. I didn’t shake one time. We came in with a good game plan and basically just attacked. We were on the same page and I think that spurred from us sitting down to talk. He made a real conscious effort to learn me during Spring Training. Being a new guy here, it was important to develop that relationship early.

“In the first couple of innings of your first [big-league] starts, you’re going to be a little excited and amped up. But after I got out of a jam in the second inning, that kind of slowed things down. I was able to settle in and work with Zuk and not try to overdo things. Pitching to thirds of the plate is what we really focused on.”

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Bob Melvin on Parker: “He’ll be getting another start [Tuesday]. If you look at his stuff, there’s a big reason that we traded who we traded for him. He was kind of the centerpiece in that deal. He had some command issues, to an extent, in Spring Training. He knew he needed to iron those things out, and he did. He pitched well [in Sacramento] and then came up and had a great first start. We feel like he’s well on his way.

“There are different ways he can get you out. It doesn’t have to be just via the strikeout. He has a real good two-seamer. He’s got a plus changeup. He’s got a slider. His curveball is coming back. I think that’s the one he was most reluctant to throw coming back off his Tommy John. I was with Arizona when we drafted him and he was the crown jewel of the Arizona organization as far as pitching goes. We felt like we were very lucky to get him.

“I don’t think [he has changed]. He still throws in the mid-90s, but with the two-seamer now, you won’t see as many mid-90s fastballs. But he’s got better movement now and he doesn’t need to throw as many pitches. Because of the two-seamer he can get some early count outs. That’s probably the biggest difference between when I first saw him and now.”