CHICAGO -- During an informal survey done among White Sox players concerning the World Baseball Classic last September, Matt Thornton was asked about his interest in taking part in the 2009 competition.

The left-handed reliever expressed a desire to pitch for Team USA but quickly added one sort of disclaimer.

"I don't think I'll be asked," said Thornton with a smile.

Apparently, the hard-throwing Thornton underestimated his full bullpen value.

On Friday afternoon, Thornton confirmed to MLB.com that he will take part in the Classic after being invited to play last Wednesday and accepting the invitation on Thursday.

Before moving forward, Thornton cleared the honor with general manager Ken Williams and pitching coach Don Cooper. Thornton will be gone from his full-time job during Spring Training for up to three weeks, starting and finishing in Glendale, Ariz., with the White Sox.

"[Williams'] concern is the players' health on our team, winning the division and making a run into the playoffs. I understand his concern," said Thornton, adding that Williams was happy for him concerning the selection.

"With that said, I prepare really well and work out hard all offseason," Thornton said. "There might be some early innings with more intensity, but it will be fun for me and break up the monotony of Spring Training. Personally, it was an opportunity where it was very tough for me to say no."

Fellow left-handed relievers Brian Fuentes and B.J. Ryan were part of Team USA's roster of 22 released on Friday. One concern for Thornton emanating from being part of this competition centers on not getting the requisite innings needed during Spring Training, especially if he finds himself third in the southpaw pecking order behind Fuentes and Ryan.

But as Thornton pointed out, the Classic's preparation and after-effect for a starter who is building toward five or six innings by the end of Cactus League action is different from the expectations for a reliever. Thornton's workload was cut last Spring Training by a minor issue with his left elbow, but it certainly didn't slow him down during the regular season. He posted a career-best 2.67 ERA in a career-high 74 games and 67 1/3 innings, striking out a single-season-best 77 and walking a mere 19.

"Really, this opportunity just blows me away," said Thornton, weighing the pluses and negatives of participating in the Classic heading into the final year of his three-year, $3.25 million deal. The White Sox hold a $2.25 million option on the hard-thrower for 2010 and a $3 million option for 2011.

"It's unbelievable to think I'll be wearing the USA on my jersey, teamed with the greatest players from the United States," he said.

Derek Jeter, Jake Peavy, Ryan Braun, Kevin Youkilis, Grady Sizemore and Dustin Pedroia are just a few of the players who will join Thornton on Team USA. J.J. Putz, Thornton's friend, former teammate in Seattle and neighbor in Arizona also will be part of the bullpen.

Actually, the two were playing golf together last week when the news came down from Thornton's agent, who had been contacted by Paul Seiler, the executive director and chief executive of USA Baseball. Thornton didn't return the call right away, but when he received a text from his agent saying that the news was pretty important, his interest was piqued.

"I'm thinking, 'Did I get traded?' " he said. "This was the last thing on my mind."

As a resident of Peoria, Ariz., Thornton was in line to get an extra six or seven weeks at home with his wife with the White Sox Spring Training base moving from Tucson to Glendale. His inclusion as part of manager Davey Johnson's roster significantly alters those plans, but he doesn't seem bothered by the extra travel.

"'Amazing' is the only way I can describe the feeling when I found out," said Thornton, who will be working with Team USA pitching coach Marcel Lachemann. "Like I said, this came as a complete surprise. It's a great honor. You can't beat it."