MESA, Ariz. — Barry Zito is returning to his roots in more ways than one.

Not only is he back with the A’s, the team that drafted him out of USC, but he also is going back to the same delivery and pitch selection that made him a Cy Young Award winner with Oakland early in his career.

Saying his “delivery degraded slowly over time” after adding the cutter to his repertoire, Zito went on to explain Saturday that the pitcher whom A’s fans will see this spring will be Zito Prime — fastball, curve, changeup, all thrown from his old over-the-top motion.

Zito, who turns 37 in May, won 23 games and the American League Cy Young Award in 2002 with that combination. The left-hander added the cutter in 2005 to combat left-handed hitters, he said, but over time that pitch came to consume him.

“It ended up that in some games I’d throw it 40 percent of the time,” Zito said.

If it were Mariano Rivera’s cutter, that would be one thing. But it wasn’t. And Zito’s cutter stole proficiency from his change and curve and took away velocity from his fastball.

“In his best years, he was more of an up-and-down pitcher,” manager Bob Melvin said, referring to the 12-6 curve Zito had coming out of college that tends to break straight down. “The cutter is more of an (inside corner) pitch.”

Melvin said he is completely on board with Zito’s pitch selection. And he liked what he saw in Zito’s first official mound performance Saturday, throwing in the first of three groups of A’s pitchers at Hohokam Stadium.

“He was very focused for a guy who’s done this a few times,” Melvin said. “I thought he threw the ball well. He threw all his pitches. He had good energy. And his curveball looked great.”

Zito, who took the 2014 season off after a seven-year stint with the Giants, has been watching video of himself early in his Oakland career to see what his best mechanics are. He also spent four months working in Houston with Ron Wolforth, the pitching guru who helped resuscitate the career of another A’s starter, Scott Kazmir.

After the Giants declined to bring him back last year after seven years in which he went 63-80 with a 4.62 ERA, Zito spent time in the past year just throwing into a net, getting what he called a “fresh perspective” on baseball and to “get the passion back.”

He has become a father, and he and his family have moved back to San Diego, where he is from, and he “got some good surfing in.” So there has been a lot happening in Zito Land. And now he is back in baseball, where he said he wants to “focus more on the cake and less on the icing.” He wants to enjoy the whole experience. So far, he has found the comeback trail rewarding.

Not that he has the A’s roster made. He is one of at least seven pitchers going for the final three spots in the rotation, so he is going to have to win a job over the likes of Jesse Chavez, Drew Pomeranz, Chris Bassitt, Jesse Hahn, Kendall Graveman and Sean Nolin. He has one Cactus League start scheduled and probably will get more, but that will have to play out over time.

Meanwhile, he changed not only his pitch selection but also his delivery. In working with Wolforth, he has streamlined his mechanics.

“When you see him throw, you notice a definite difference,” Wolforth told this newspaper. “The old hook he had where he went behind his back during the windup, that’s gone. We didn’t set out to eliminate the hook, but it’s a process of taking links out of his personal bicycle chain to make him more efficient as a pitcher.”

Zito said he has gone back to delivering the ball the way he used to, adding that all his pitches should benefit from having more spin on them.

“My body is more efficient now, and I feel like I have a little more life on the ball,” he said. “More than anything, the spin on the ball is back. It’s not something they talk about a lot, but they’re going to be talking about it.”

Zito has groomed himself to return as a starter, and the A’s are looking at him that way. Left unsaid is whether Zito would be willing to start the season at Triple-A Nashville if he doesn’t make the rotation out of camp.

Pitchers Bassitt, Tyler Clippard and Ryan Cook got high marks from Melvin based on their first throwing sessions of the spring.

Melvin was in awe of 20-year-old third baseman Renato Nunez, who hit two balls over the towering scoreboard in left field in batting practice and two more off it. The manager said of Nunez, who hit 29 homers for Class-A Stockton last year: “We saw him last year as a 19-year-old come up here and get a couple of at-bats and have no fear at all. When I was 19 I was hiding in the bullpen, catching bullpens and trying not to be noticed where he’s out here, definitely wanting to be noticed. It looks like he has quite a future ahead of him.”