FORT MYERS, Fla. — Red Sox left-hander Jon Lester finalized a $30 million, five-year contract today, a deal that could be worth $42.75 million over six seasons if Boston exercises a club option for 2014.

"We're extremely happy to have gotten this done," Red Sox general manager Theo Epstein said. "Jon is already a big part of this organization, and we project him to play an even greater role going forward."

After being diagnosed with cancer in 2006, Lester came back to go 4-0 in 2007 and then 16-6 with a 3.21 ERA last year. He threw 210 1-3 innings and made 33 starts — both team highs — in his first full season in the majors. He ranked among the AL leaders in shutouts, ERA, starts, innings and wins.

Boston's second-round pick in 2002, Lester pitched a no-hitter May 19 against the Kansas City Royals at Fenway Park. He also won the clinching game for the Red Sox during their 2007 World Series sweep of Colorado.

He is the third homegrown Red Sox player to sign a long-term contract recently. Second baseman Dustin Pedroia and first baseman Kevin Youkilis came to terms this offseason, and closer Jonathan Papelbon agreed to a one-year deal in January.

"It's a great organization. Besides the Yankees, it's the most storied organization in baseball," Lester said.

"The coolest part about this place is that you come up through the system with guys like Pedroia and Youkilis and Pap, and it's fun to see them succeed, and be on the same team, and win a World Series together, and hopefully win some more."

Lester said that with contract pressures now behind him, he and his family are free to relax, and he can continue working toward another World Series title with his teammates.

Boston manager Terry Francona has watched Lester's progression over the last few seasons since the lefty made his big league debut June 10, 2006, and his battle with cancer, which began later that summer.

"I don't know if any of us know where he's going to end up," Francona said. "I don't think he's ever going to stop wanting to get better. We already think he's pretty good."

Francona said Lester was one of baseball's best pitchers in the second half last year.

"We all look to his size, his delivery, his work ethic, as somebody who can be very durable," the manager said. "He's a competitor on the field, he's a great kid off the field, as everybody knows."

The deal replaces a one-year contract Lester agreed to last week that called for a salary of $525,000 in the major leagues and $252,900 in the minors.

Lester gets $1 million this year, $3.75 million in 2010, $5.75 million in 2011, $7,625,000 in 2012 and $11,625,000 in 2013. Boston has a $13 million option for 2014 with a $250,000 buyout.

If Lester finishes first or second in Cy Young Award voting during any of the next five seasons and is traded, the option would be voided.

Epstein said a contract extension with left fielder Jason Bay, whom the Red Sox acquired from Pittsburgh at the trade deadline last year, appears unlikely at this time.

Bay is entering the final season of a four-year, $18.25 million contract that he signed in 2006 with the Pirates.