Carpenter and the Cardinals came to the difficult decision after symptoms returned following a pair of throws the past week. He will have the surgery on July 19 and hopes to be ready to pitch by the beginning of spring training next year.
The right-hander, who was recently diagnosed with thoracic outlet syndrome, has yet to appear in a game this season since being shut down in spring training.
"It was a tough decision, no question about it," Carpenter said. "But I did everything I could to see if I could get back. Personally it's a good thing because it's got answers. I went down and saw Dr. Pearl on Thursday and he really believes that he can fix all these issues that I've been dealing with since 08. Hopefully it's a fact.
"I still want to pitch again and this is going to be the way for me to pitch again. We've tried since spring training to get this going and every time I try to come back, unfortunately it just doesn't allow me to do that."
A visit to Dr. Gregory Pearl in Dallas last week confirmed that the right-hander has thoracic outlet syndrome, a rare condition that includes pain in the neck and shoulder, numbness and tingling of the fingers and a weak grip.
Carpenter was hoping to pitch through the condition the rest of the season but acknowledged that surgery might be the only way to prolong his career.
"We were out of answers so we went down there and I left wanting to throw and wanting to continue to pitch, but also very excited knowing that if it didn't work there was finally an answer for me," Carpenter said. "Since 2008 it just continued to get worse and I think we just hit the peak and we weren't able to get it back to where we wanted to.
"The way that he presented it and spoke about the results and what he feels he can bring me and offer me, I ultimately couldn't say no. It's my obligation to do everything I can to get out there. I feel obligated to my team, the fans, the organization, Mr. DeWitt and everybody that trusts and hopes you can do everything you can to get out there and pitch and help this team get another World Championship."
The ace first reported neck stiffness and pain following a workout March 3. He had a cortisone injection to alleviate the pain, and returned to the bullpen mound nearly two weeks later.
But his arm didn't respond after another workout a few days later and he returned to St. Louis for a new round of tests. He spent the next several weeks strengthening his shoulder before finally being cleared to begin throwing the final week of May.
Carpenter, who turned 37 in April, was progressing steadily before his shoulder didn't respond following his first throw to hitters on June 22 in Kansas City. He attempted another throw from the Busch Stadium bullpen mound on Friday before deciding to shut it down.
Had Carpenter not received an encouraging outlook from his visit to Dr. Pearl, Carpenter had begun to contemplate retirement.
"Yeah, there's no question about it," Carpenter said. I had done everything I could and everybody upstairs did everything they could. Every time I tried to come back and throw – and I can go out and throw, I can play catch - but to ramp it up and throw it at the level I need to throw it at, it just didn't work.
"I asked him one simple question. I said 'I'm 37 years old. I've had a nice career. Is this worth getting this done?' His comment to me was he's seen me pitch, he knows I can still pitch. He said he did Kenny Rogers when he was 36 years old and he continued to pitch successfully for like five or six years. He said there's no question he believes that I can come back and be as strong as ever.
Carpenter threw more than 270 innings in the 2011 regular season and playoffs, the most of any pitcher in baseball. He threw 36 grueling innings in the postseason, including two starts with just three days of rest and three World Series starts.
The veteran right-hander surpassed the 4,000-pitch mark for the first time in his career, finishing with 4,155. He signed a two-year, $21 million extension with the Cardinals in September.
Carpenter has now missed nearly five full seasons due to injuries in his career.
"Two or three weeks ago we were much more optimistic and thought there was a chance he would pitch again this year," said general manager John Mozeliak. "But given the outcome of that bullpen in Kansas City, it became pretty clear that if he was going to pitch, it was going to be a very painful experience for him."
He went 11-9 with a 3.45 ERA in 34 starts last season. He's 144-92 in 14 big league seasons with a 3.76 ERA. He won the 2005 Cy Young Award and has won at least 10 games in nine different seasons.
With left-hander Jaime Garcia also on the disabled list, the Cardinals will likely be in the market for a starting pitcher as the July 31 trade deadline approaches. And bringing clarity and a finality to Carpenter's situation may get that ball rolling.
"I think if we could find starter help, that would be a benefit for us," Mozeliak said. "You look at our rotation and the high volume that Wainwright is having to throw under, the volume Lance Lynn is throwing under, when you start to look long term, we want to make sure we are smart about that. As we look to the trading deadline, if we could find a starter that would make sense for us."
It's the second season in a row that the Cardinals will have gone the entire year without one of their top pitcher throwing a single pitch. Adam Wainwright missed all of 2011 due to Tommy John surgery after winning 20 games the previous year.
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