Lester, who was 22 at the time, swiftly went to work on treating his cancer and underwent six rounds of chemotherapy treatment. To this point, there have been no recurrences, and Lester went on to win a World Series, pitch a no-hitter and make it to a couple of All-Star Games.
But there is not a cure for everybody, and that's why Lester and the Red Sox continue to work actively in the fight against cancer.
For more than a half-century, the Red Sox have held a partnership with the cancer-fighting Jimmy Fund, and each year, players from the team are active in a telethon and other events which help raise millions to help find cures for cancer.
The Red Sox joined a unique and league-wide baseball initiative on Monday at the Winter Meetings.
These Winter Meetings include an MLB.com Auction to benefit Stand Up To Cancer, which MLB has supported since 2008 as founding sponsor. Public relations representatives from all 30 clubs were inspired to act based on individual club members impacted by the disease, and they jointly organized the auction and announced it Monday in Nashville with MLB staff.
Bidding closes at 11:59 p.m. ET on Thursday, with more than 70 baseball-related experiences ranging from clubhouse tours by players to lunches with general managers to team bus rides to meet-and-greets with 14 Hall of Fame players.
The Red Sox have put some intriguing items up for auction.
The first is a chance to sit behind the Green Monster for three innings, while also getting the opportunity to watch batting practice at Fenway Park and meet a Red Sox player. That package includes four infield grandstand tickets.
The second item is lunch for four with manager John Farrell in the team's clubhouse. Imagine sitting there in Boston's clubhouse and getting to pick Farrell's brain on the inner workings of the club.
And the third item is the copy of the must-have Fenway 100 book, signed by Hall of Famer Jim Rice.
Perhaps no Red Sox player has better perspective than Lester. Sure, he had the worst season of his life in 2012, but he knows that a bad baseball season pales in comparison to the fight against cancer.
"It feels like a lifetime ago [that I was diagnosed]," said Lester. "And I try not to think about it. But I did use it to get through some of my personal struggles and how I pitched this season. I wasn't going to let myself start thinking, 'Woe is me.' It certainly helped keep things in perspective."