BOSTON (CBS) — As Theo Epstein officially leaves Boston to take over as president of baseball operations for the Cubs, he says in an op-ed in the Boston Globe that his departure had nothing to do with the Red Sox’ “crushing” September collapse.

In the op-ed published Tuesday morning, Epstein said he planned to leave the Red Sox in 2012 when his contract expired, despite an attachment to Boston and the Red Sox that dated back to his boyhood.

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But, Epstein wrote, the departure of manager Terry Francona after the Red Sox’ “collective failure” last month made him think that it would be better if a new general manager picked a new field manager.

“So, knowing my time as the general manager was drawing to an end, I had a decision to make: stay one more year and do my best to conduct the manager’s search under less than ideal circumstances, or recommend the succession plan, allow (assistant general manager) Ben (Cherington) to run the search process, and join the Cubs. I wrestled with leaving during a time when criticism, deserved and otherwise, surrounded the organization,” Epstein wrote.

But Epstein said he considered the words of football legend Bill Walsh, that coaches and executives should look for change after 10 years with one team.

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As to the “collective failure,” Epstein conceded that he was “the person ultimately responsible.”

“But the reports about team-wide apathy and indulgence are exaggerated. It may not seem this way now, but the team did care about winning, about the fans, and about each other; unfortunately, we failed when we let less important things get in the way,” he wrote. “I tried desperately to reverse our slide, as did (Francona), the coaches, and the players. But we just could not play well, and then we did not handle the adversity well.”

Epstein said Cubs, with their “passionate fans, dedicated ownership, tradition and World Series drought represented the ultimate new challenge.”

He ended by saying he hoped the Red Sox and Cubs meet in the World Series in the near future.

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The Cubs will formally introduce Epstein at 11 a.m. will carry the news conference live.