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Chicago, IL (SportsNetwork.com) - Jon Lester was introduced to the media by the Chicago Cubs on Monday.

Lester agreed to terms on a six-year contract reportedly worth $155 million. The deal includes a vesting option for the 2021 season.

"I got a good sense of how crazy these fans are about their Cubs baseball," Lester said at a downtown Chicago press conference. "It's a huge honor to be part of this organization. We fully buy in, and we take on the responsibility of trying to bring this city a World Series."

The 30-year-old Lester went 6-4 with a 2.35 earned run average for the Oakland Athletics after he and outfielder Jonny Gomes were acquired in a blockbuster trade-deadline swap from the Red Sox for outfielder Yoenis Cespedes.

Lester is most known for his prowess in the postseason, where he is 6-4 with 2.57 ERA in 14 career appearances (12 starts), including a perfect 3-0 mark with a sparkling 0.43 ERA in the World Series.

Lester has a 116-67 record with a 3.58 ERA over his nine-year career.

He turned down a $70 million contract extension from Boston during the spring, the team which he helped win two World Series titles (2007, 2013).

"This signing really marks a transition of sorts for the Cubs, the start of a period where we are clearly very serious about bringing a World Series to the Cubs and the people of Chicago," president of baseball operations Theo Epstein said. "It's a great day for our fans. They've been so patient with us, incredibly patient, over the last few years and they truly deserve a pitcher and a person of this caliber to call their own."