The 37-year-old Posada is currently on a throwing program in Tampa, Fla., rehabilitating the right shoulder strain that cost him most of last season. Posada underwent surgery July 30 and the Yankees are counting on him as their starting backstop next season.
"I am sure he would love to play [in the World Baseball Classic], but he is currently rehabbing from surgery and would not be ready," Yankees general manager Brian Cashman said.
Reports out of Puerto Rico indicated that Posada has started training for the tournament, concurrent with his rehab to prepare for the Yankees' season.
In a Spanish-language interview with Primera Hora, Posada said that he is especially motivated to get into the tournament since he may no longer be an active player for the next one in 2012.
"This will be my last chance to play for Puerto Rico, and I'm very clear on that," Posada said. "For that reason, I'll do anything possible to be 100 percent, because it is a dream of mine to wear that uniform."
Posada estimated that his recovery from the July 30 surgery is at "75 percent," though he is batting and throwing without problems.
Posada's father, Jorge Sr., told The Associated Press that his son has already signed a participation agreement for the Classic.
"He feels fine and wants to play for Puerto Rico," Posada Sr. reportedly said.
The interest, it would seem, is mutual. In an e-mail to MLB.com, Lou Melendez -- the general manager of Puerto Rico's Classic team -- wrote: "I would love to have Posada on Team PR. I am waiting to learn his status because of insurance issues."
Posada only started a throwing program on Dec. 8, which all reports have indicated is progressing fine. He could potentially serve as a designated hitter for Puerto Rico -- Posada was able to hit but not throw during extended stretches for the Yankees last season, before he was placed on the disabled list for the first time in his career.
But with the Yankees importing a pair of top-flight starters in CC Sabathia and A.J. Burnett this offseason, the importance of Posada's presence to help guide the pitching staff would give the Yankees an easy reason to nix his Classic participation.
"Obviously, he's very important to this club," Yankees manager Joe Girardi said recently. "We need him. I'm encouraged right now. ... You can talk about playing three out of four [games] or four out of five, but I think early on the important thing is that we don't abuse him, and allow him to continue to gain strength in that shoulder. I plan on him being our everyday catcher."
Yankees media relations director Jason Zillo also confirmed that Posada will not play in the tournament. The only Yankees currently slated to play in the Classic are Derek Jeter, who will represent the United States, and Alex Rodriguez, who will switch teams and play for the Dominican Republic.
While Mariano Rivera will not be ready to represent Panama after having surgery to remove a calcified AC joint in his pitching shoulder, Johnny Damon and Joba Chamberlain are also among those who have expressed interest in playing for the United States.
The switch-hitting Posada was limited to 51 games last season, batting .268 with three home runs and 22 RBIs in the first year of a four-year, $52.4 million deal.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.