Both teams announced the deal Sunday night, though neither disclosed the amount of cash involved.
In exchange for Burnett, the Yankees get 25-year-old right-hander Diego Moreno and 20-year-old outfielder Exicardo Cayones, both low-level prospects. The Pirates will pay $13 million of the $31.1 million remaining on Burnett's contract, sources told ESPN The Magazine's Buster Olney (Burnett is on a year-round contract and already has been paid $1.9 million in 2012).
The teams agreed to the trade Friday but it was subject to Burnett passing a physical, which he did Sunday at Pirates camp as pitchers and catchers held their first workout of spring training in Bradenton, Fla.
Commissioner Bud Selig also had to approve the deal because of the money involved.
"A.J. Burnett is a solid veteran starting pitcher with an above average pitch repertoire and potential
to provide us with significant quality innings from our starting rotation," Pirates general manager Neal Huntington said in a statement released by the team.
Burnett goes from a perennial World Series favorite to a club coming off its 19th consecutive losing season, a record for the four major pro sports in North America.
"I think he's looking forward to the opportunity to re-establish himself and mentor some of the young pitchers," said Burnett's agent, Darek Braunecker.
Asked to assess the Burnett Era on Sunday morning, Yankees general manager Brian Cashman -- who signed Burnett as a free-agent to a five-year, $82.5 million contract before the 2009 season -- declined to comment.
"In fairness to everyone, A.J., the Pirates, the Yankees, I'm going to steer clear of that for now," Cashman said. "Right now, he's still a Yankee."
Reached by phone Sunday night, Cashman said he would address the issue on Monday.
"Believe me, it won't be a bash," he said.
Burnett's record as a Yankee was 34-35 with a 4.79 ERA in 99 starts. His high point came in Game 2 of the 2009 World Series at Yankee Stadium, when he outpitched Philadelphia's Pedro Martinez to even the series after Cliff Lee had beaten the Yankees in Game 1. That victory enabled the Yankees to go on and win their 27th World Championship five nights later.
After going a creditable 13-9 with a 4.04 ERA in his first season as a Yankee, Burnett went 10-15 with a 5.26 ERA in 2010 and 11-11 with a 5.15 ERA in 2011. Both seasons were marked by severe second-half declines; over the past two Augusts, Burnett was 1-6 with a 9.56 ERA. He also set a franchise record with 25 wild pitches in 2011, bringing his three-year total to 58, the most by a major league pitcher since Tony Cloninger uncorked 62 between 1964-1966.
Burnett became expendable when the Yankees acquired Michael Pineda from Seattle in a trade and agreed to a one-year deal with free-agent pitcher Hiroki Kuroda. They joined holdovers CC Sabathia, Ivan Nova, Phil Hughes and Freddy Garcia in a crowded rotation.
In Pittsburgh, Burnett joins a rotation that includes newly signed Erik Bedard and returnees James McDonald, Kevin Correia and Jeff Karstens. Charlie Morton is recovering from hip surgery in October. When Morton is available, Karstens could return to the bullpen and spot starts.
"Having played in New York, I can say that playing in Pittsburgh is ... I wouldn't say easier, but just the pressure and everything that comes along with it is less," said Karstens, who also pitched for the Yankees. "That should make his transition here a little bit easier. Anytime you can add a quality arm like that to the staff, it's going to make us better."
"With the relationship we've had, the fact that we worked together and did well together, it made me feel we can get back to where it was that year. Even after he left Toronto for New York, we constantly had conversations. He's a joy to be around. He brings good energy. I think he's going to fit in well here."
Moreno was 2-4 with a 3.21 ERA and 31 strikeouts in 33 2/3 innings last year during 34 relief appearances for Bradenton of the Florida State League and 0-0 with a 4.91 ERA in seven games with Double-A Altoona.
Cayones was 2 for 32 (.063) for State College of the New York-Penn League and 24 for 98 (.293) with no homers and 12 RBIs for the Gulf Coast Pirates last year.
Wallace Matthews covers the Yankees for ESPNNewYork.com. Information from The Associated Press was used in this report.