Lester was selected by the Boston Red Sox in the second round of the 2002 MLB June Amateur draft and made his big-league debut in June 2006. Just months into his MLB career though, the southpaw was diagnosed with anaplastic large T-cell lymphoma and underwent chemotherapy.
The 200-game winner was able to return to the Red Sox midway through the 2007 season, though, went 4-0 down the stretch and helped Boston win its second World Series in four years by tossing 5 2/3 scoreless innings in the Game 4 clincher.
"I was in Triple-A on a rehab assignment in Pawtucket after cancer," Lester said, per ESPN's Jesse Rogers. "My parents were there and they were leaving that day or the next day to go home, and I told them they have to change their flight and I said, 'I'm starting the next night in Cleveland.' ... That's one of the top moments of my career. Seeing their faces was pretty cool. Once I got back to baseball, I tried not to take anything for granted and really appreciated being around the guys."
Lester then went on to put together arguably the best stretch of his career from 2008 through 2014, winning at least 15 games in five of the next six seasons and making his first two All-Star appearances. The 38-year-old went 19-9 with a 3.25 ERA and league-best 9.7 strikeouts per nine innings mark in 2010, finishing fourth in the AL Cy Young vote.
After a down season in 2012, Lester and the rest of the Red Sox bounced back big time in 2013, using the mantra "Boston Strong" throughout the year following the Patriots' Day Boston Marathon bombings to propel them to another World Series championship.
Lester made his third All-Star team in 2014, but was traded with outfielder Jonny Gomes to the Oakland Athletics for outfielder Yoenis Cespedes that summer. The Tacoma, Wash., native spent the 2015 through 2020 seasons with the Chicago Cubs, earning two more All-Star nods, finishing as the NL Cy Young runner up in 2016, and helping the franchise break a 108-year championship drought as well. The lefty spent the 2021 season split between the Washington Nationals and St. Louis Cardinals.