CHICAGO — He’s one of the biggest free agents not only in the history of the Cubs but also in the proud history of Chicago professional sports. But after a decorated career that included six seasons on the North Side, Jon Lester is calling it a career.

The pitcher announced his retirement on Wednesday morning to ESPN.com reporter Jesse Rogers, bringing an end to a celebrated tenure for the pitcher who had stays with five teams in Major League Baseball.

“It’s kind of run its course,” Lester told Rogers in the article. “It’s getting harder for me physically. The little things that come up throughout the year turned into bigger things that hinder your performance.”

Lester joined the Cubs in 2015 as the club’s first major signing in the Theo Epstein era, signaling the team’s desire to begin to compete for championships after a hefty three-year rebuild to start his tenure. The starter was a catalyst to the team’s turnaround, aiding the Cubs’ run to five postseason appearances in six seasons.

That included three appearances in the National League Championship Series in his first three seasons and was critical in the team’s run to a World Series title in 2016. In helping to break the clubs’ 108-year title drought, Lester was a Cy Young Award finalist and an All-Star as he went 19-5 with a 2.44 ERA.

In that postseason, he was named the NLCS co-MVP with Javier Baez while also keeping the Cubs alive in the World Series against Cleveland with a Game 5 win at Wrigley Field. Lester also appeared in relief in Game 7 in which the Cubs won 8-7 to clinch an elusive World Series championship.

Lester led the National League with 18 wins in 2018 as he was elected to another All-Star team and would go onto pitch two more seasons in Chicago before he joined the Nationals to start 2021. He was traded to the St. Louis Cardinals at the trade deadline, making 28 starts between the club in his final year in the MLB, going 7-6 with a 4.71 ERA.

Lester finished his tenure in Chicago with a 77-44 record with a 3.64 ERA in 171 appearances.

Before coming to Chicago, Lester had another celebrated run as a member of the Red Sox, pitching for that organization for nine seasons. He was a three-time All-Star in Boston and helped the organization to World Series championships in 2007 and 2013. He finished with the same ERA with the Red Sox that he did with the Cubs – 3.64 – while going 110-63.

In 2014, with the Red Sox out of playoff contention, Lester was traded to the Athletics for their postseason run, going 6.4 with a 2.35 ERA.