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Oakland Athletics' starting pitcher Trevor Cahill delivers against the Detroit Tigers in the first inning of an MLB game at O.co Coliseum in Oakland, Calif., on Friday, Sept. 16, 2011. (Ray Chavez/Staff)

The A's kicked off their latest roster makeover Friday by trading pitchers Trevor Cahill and Craig Breslow to the Arizona Diamondbacks.

Oakland received pitchers Jarrod Parker and Ryan Cook and outfielder Collin Cowgill, three prospects who could play significant roles for the A's in 2012.

Cahill's name surfaced Wednesday as a trade possibility. Until then, it was fellow starter Gio Gonzalez and closer Andrew Bailey who were most heavily rumored to be leaving Oakland. Both remain strong candidates to be dealt, with Texas interested in Gonzalez.

"It's never easy to trade a guy who was a focal point of your team for three years," A's assistant general manager David Forst said of Cahill. "But we understand every so often you need to shuffle the deck."

Cahill broke into the A's rotation in 2009, a 21-year-old who appeared part of the foundation upon which the team would build. He went 18-8 with a 2.97 ERA in 2010 and was an All-Star. Last April, he signed a five-year, $30.5 million contract extension with club options for 2016 and 2017.

That affordable, long-term contract was attractive to the defending National League West-champion Diamondbacks, who will add Cahill to a rotation that includes Daniel Hudson, Josh Collmenter and Ian Kennedy.

"We think we've got four young starters who are as good as anybody in the N.L. West," Arizona G.M. Kevin Towers said.

The A's are looking to stockpile prospects -- cost-controllable and with little big league service time -- who can develop together as the team hopes to build a new ballpark in San Jose.

Cahill took news of the trade hard. He said he was happy with Oakland and looked forward to being reunited with pitching coach Curt Young, who returned to the A's after one season with Boston.

"Maybe another piece or two and we would have had that core thing and been good for a long time," Cahill said. "You kept thinking in the future, and then, all of a sudden, it passed you up, and now you're on a new team."

In Parker, 23, the A's get a right-hander rated as Arizona's No. 4 prospect by Baseball America. He was their top prospect before missing the entire 2010 season because of "Tommy John" elbow surgery.

He went 11-8 with a 3.79 ERA last season for Double-A Mobile. In his only big league start, Parker threw 52/3 shutout innings against the Dodgers in September.

He has a fastball that reaches 95-96 mph, a good changeup and an overhand curve that he has yet to completely regain the feel for after surgery.

"It's not out of the question he could pitch well in spring training and start the year in the rotation," Forst said.

Cowgill, 25, has played in just 36 major league games, but Forst said Cowgill will get every chance to win the center field job. That's no surprise given the lack of depth and experience in the A's outfield.

One scout interviewed for this story gave Cowgill high marks for his grittiness but said he doesn't possess one dominant "tool" that stands out.

Cook, 24, became a full-time reliever last season. A right-hander, Cook has hit 97 mph with his fastball, and the A's believe he might be suitable for late-inning work this season.

Breslow had been a workhorse for the A's bullpen since being claimed off waivers from Minnesota in 2009. By the time Forst called to tell him he'd been traded, the lefty had already heard from another source.

"I can no longer denounce the relevance of Twitter," Breslow tweeted. "It broke the story of my trade ... to me."