CHICAGO -- Jon Lester took pride in staying on the mound until he had given everything he had on any given day. After 16 seasons, three World Series rings and a career spent as one of the best left-handers of his generation, Lester is giving up the ball.

On Wednesday, Lester announced his retirement via a report by ESPN, acknowledging that the physical toll of a baseball season was becoming increasingly challenging. So the big lefty is stepping aside after a remarkable run of consistency and October dominance.

• Roundtable: Is Lester a Hall of Famer?

"It's kind of run its course," Lester told ESPN.com. "It's getting harder for me physically. The little things that come up throughout the year turned into bigger things that hinder your performance.

"I'd like to think I'm a halfway decent self-evaluator. I don't want someone else telling me I can't do this anymore. I want to be able to hand my jersey over and say, 'Thank you, it's been fun.' That's probably the biggest deciding factor."

Lester's legacy includes forever being an icon in two of baseball's most storied cities: Boston and Chicago. The lefty was part of two World Series championship teams with the Red Sox (2007 and '13) and famously helped the Cubs erase their 108-year title drought in 2016.

• Lester in WS Game 5: A win above all others?

Over the course of his career, Lester was a five-time All-Star, won 200 games, authored one no-hitter (May 19, 2008) and finished in the top four in Cy Young Award balloting in three seasons. His signature cutter carried the day, but his fierce competitiveness was his calling card.

In an era of specialization, Lester won at least 15 games eight times and logged 200 or more innings in eight campaigns. As a testament to his consistency, Lester had the same ERA (3.64) for the Red Sox (nine seasons) and Cubs (six seasons).

"Being out there, being able to take the ball every fifth day, staying healthy," Cubs manager David Ross said of Lester in September, "it allows you to continue to work through competition and adjust and find a way to win. He's been a winner his whole life, so there's no secret that he was going to figure out a way to have success."

Lester showed perhaps even more toughness and determination off the field than on the mound. He was diagnosed with anaplastic large T-cell lymphoma during his rookie season in 2006, and he returned to the big leagues in July of the next season, picking up a win over Cleveland in his first game back.

"I was in Triple-A on a rehab assignment in Pawtucket after cancer," Lester told ESPN.com. "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. 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."

The first of two World Series triumphs followed in that 2007 season, and then the no-hitter in '08. Lester won 110 of his 200 games with the Red Sox, who traded him to the A's at the Trade Deadline in '14. That winter, Lester hit the open market just as the Cubs were emerging from an extensive rebuild.

During the Winter Meetings that offseason, the Cubs punched the gas on their contention timeline by signing Lester to a six-year, $155 million pact. After the deal was struck, former Chicago manager Joe Maddon famously told reporters, "We won the baseball lottery."

Lester immediately helped the Cubs reset the culture around the ballclub, bringing an edge of competitiveness, relevance and expectation. In six seasons on the North Side, Lester won one World Series, three National League Central titles, reached the NL Championship Series three times and helped the club make the playoffs in five years.

"We owe him a great debt of gratitude," former Red Sox and Cubs executive Theo Epstein said after the 2020 season. "We were investing in Jon Lester the person every bit as much as we were investing in Jon Lester the pitcher. And he came through in both areas for us in typical Jon Lester fashion."

On the October stage, all Lester did was piece together a tidy 2.51 ERA over 154 innings across 26 career games.

In six World Series appearances, Lester was even better, turning in a 1.77 ERA with four victories. He won the clincher against the Rockies in 2004, won both starts in the '13 win over St. Louis, and worked three relief innings in Game 7 of the '16 Series (after starting Games 1 and 5).

Lester made a dozen Game 1 or Wild Card Game starts in the playoffs, started one Game 7 and was the co-MVP of the 2016 NLCS against the Dodgers.

When it comes to Lester's chances for the Hall of Fame, here are some statistics to support his case:

• From 2006-21, which covers Lester's career, only Justin Verlander and Zack Greinke registered more wins or innings. That makes Lester first among all left-handers in those categories during that span. He ranked sixth overall in strikeouts during that time period.

• Lester is one of 85 pitchers to reach at least 2,000 strikeouts in his career. He ranks 40th on baseball's all-time list, but 12th among left-handed pitchers.

• Only 27 pitchers (seven lefties) in the Modern Era (since 1900) have logged at least 12 seasons with 31 or more starts. Lester compiled his dozen such tours consecutively from 2008-19.

• Lester is one of 57 pitchers to have at least 200 wins and 2,000 strikeouts in a Major League career. Only 12 on that list, including Lester, have a winning percentage of .630 or better.

• Only 18 left-handers have reached a minimum of 200 wins and 2,000 strikeouts, with just Randy Johnson (.646) and Lefty Grove (.680) ranking better than Lester (.631) in winning percentage.

• Roundtable: Is Jon Lester a Hall of Famer?

The trade out of Boston robbed Lester of a proper sendoff with Red Sox fans, though he did take out an ad in the Boston Globe to offer his gratitude. In Chicago, Lester bid farewell to Cubs fans in more fitting fashion, picking up the tab over three days after the 2020 season for fans who told a few bars to "put it on Jon's tab." Lester wound up buying nearly 5,000 Miller Lites for Cubs fans.

Lester pitched twice at Wrigley Field last season -- once with the Nationals and later for the Cardinals -- and Ross, his former personal catcher in Boston and Chicago, quipped that the City of Chicago should have dubbed his May 17 return "Jon Lester Day."

No one caught more of Lester's career innings than Ross, whose first mound visit as the Cubs' manager in 2020 was amusingly to pull the lefty from a spring game. Ross was thrilled last season to see Lester reach 200 wins -- a goal the pitcher was unable to achieve with the Cubs due to the previous pandemic-shortened season.

"There's nobody that's done more for me in my career than that human being," Ross said near the end of Lester's tenure with Chicago. "What he means to me and my family and the things he's done for me, as part of my career, I wouldn't be sitting in this seat without that guy."

Behind the scenes, Lester took a cue from the veterans he was around early in his career and was generous with his teammates. He allowed them to use his suites on the road and picked up the tab. Lester was known to give bottles of champagne for career milestones, or take a young player suit-shopping after reaching the big leagues.

Lester's teammates, coaches and managers will recall those moments, along with the fiery exchanges in the dugout or on the field in the heat of competition over the course of a decorated and dominant career. Ross was asked last season what Lester left behind in Chicago's clubhouse.

"He brought a championship mentality," Ross said, "and a preparation and hard work that he expected every day, that he held himself accountable for, and that he was brought up knowing how to do. He brought that here, and winning followed."