Dempster said Sunday he is stepping away for physical reasons and to spend more time with his family. But he left a slight opening to play in 2015.
"I had an incredible run, a chance to play 16 years in the major leagues and be around a lot of great teammates, made a lot of good friendships, great friendships," Dempster said one day before the first formal spring training workout for pitchers and catchers. "I'm totally comfortable with it. I'm at peace with my decision."
Dempster, whose contract expires after this season, finished his only year with the Red Sox with an 8-9 record and a 4.57 ERA and didn't get a start during their postseason run to a World Series title.
"The past few years have been tougher and tougher," he said. "As you get older, going through some things, some issues I have with my neck that have made it harder and harder to throw a baseball and throw it like I'm accustomed to throw it" contributed to his decision.
And, he said, "I've got three amazing children that I want to watch grow up and be around."
The Red Sox still have a solid veteran rotation with Jon Lester, Clay Buchholz, John Lackey, Jake Peavy and Felix Doubront, and several promising young starters. If they're seeking a veteran to add depth, they could consider right-handed free agents Ervin Santana and Ubaldo Jimenez.
"I like the staff that we have," manager John Farrell said.
Several teammates watched as Dempster made his announcement, including Lester, Buchholz, Lackey, Peavy, first baseman Mike Napoli, second baseman Dustin Pedroia, catcher David Ross and reliever Andrew Miller.
"Everybody wants to soak in their last moments of being around him," Miller said. "He's a great guy. He left quite his mark and will be remembered fondly around here."
The decision, Miller said, "was a shock to everybody."
Dempster said he spoke with the club a few weeks ago about taking the season off.
And what about 2015?
"I don't know yet," he said. "If something changes then, obviously, something changes, but I don't see that changing."
Dempster pitched with the Florida Marlins, Cincinnati Reds, Chicago Cubs, Texas Rangers and Red Sox. He is 132-133 with a 4.35 ERA and made the All-Star team in 2008 when he went 17-6 with a 2.96 ERA with the Cubs. He was Chicago's closer from 2005-07, totaling 85 saves.
He began the 2012 season with the Cubs then went to the Rangers at the trade deadline.
Boston signed Dempster to a $26.5 million, two-year deal before last season. He will lose half that amount by sitting out this year.
"The money was not that much of a difficult decision," he said, but "I'm a little sad that I won't be around" his teammates as they try to defend their championship.
"There aren't too many people who could say that the time is right to walk away from a game that I love, that's treated me so well," Red Sox reliever Craig Breslow said, "and particularly when there's a pretty sizeable amount of money that's being left on the table."
General manager Ben Cherington said Dempster told him of the decision about 10 days ago.
"It came out of left field," Cherington said.
Players didn't find out until Sunday.
"At first I didn't really know what to say. It caught me off guard," Napoli said. "That's how everyone wants to go out, on their own terms."
Dempster was praised for his upbeat personality that helped the Red Sox recover from a collapse at the end of the 2012 season and transform the clubhouse into a positive place. Farrell also admired the way he accepted his demotion from the rotation for the postseason.
"A consummate team player," Farrell said.
While Dempster struggled at times on the field last year, he kept the clubhouse loose.
"His comedic value will be sorely missed," Miller said.
Dempster pitched just one inning in the World Series, a scoreless ninth in Boston's 8-1 win over St. Louis in Game 1. He ended it by striking out Matt Adams.
"If this is the end, then this is the end, and what a great way to go out," Dempster said.
Notes: The Red Sox signed right-hander Francisco Cordero to a minor-league contract with an invitation to the major-league camp. A closer for most of his career, he didn't pitch last year after struggling in 2012. In 14 seasons with six teams, he is 47-53 with a 3.38 ERA and 329 saves. ... Miller and the Red Sox agreed to a one-year contract worth $1,903,125, avoiding arbitration. Miller had asked for $2.15 million and had been offered $1.55 million. He made $1,475,000 last year. Boston has no remaining players in arbitration.