Cherington's relationship with Lester has long been a strong one. On Thursday, he had to tell him he was headed to the Oakland Athletics for Yoenis Cespedes.
"My last conversation with him was in the clubhouse. He came in to clear some stuff out, so I got a chance to go down there and see him in person today," said Cherington. "That was a thank you and an appreciation for everything he's done and a good luck. He's going to a new place and he's going to be pitching in big games down the stretch and he'll have an opportunity to win again, so we'll be rooting for him.
"Prior to that, I'd been trying to keep him abreast as well as I can about what was going on. I couldn't do that perfectly, but I tried to. I've had several conversations with him really going back two or three weeks now. The last one was today. He and [Jonny] Gomes were in the clubhouse together, and I got a chance to see both of them in person before they left.
"It's not easy. And it's not easy for him, not easy for everyone. But I think everyone understands that everyone is trying to make something better. Jon Lester's trying to make something better for himself, we're trying to make something better. Underneath it all, people understand that. But going through it is hard."
In the days before he was traded, Lester said he would still want to pursue a return to the Red Sox as a free agent even if he was dealt.
"He's an Oakland A right now," said Cherington. "So I don't think it's right for me to talk about that other than to say, looking back that we certainly had a desire to engage on a contract conversation with him and that conversation didn't happen enough for whatever reason.
"As we got deeper into the season, he made it clear that that wasn't something he wanted to focus on right now, and so we honored that desire on his part. And I had a conversation with Jon about that that we respected that position but because of the performance of the team that meant we both might have to deal with this possibility.
"If the team's performance didn't really improve that meant teams were going to start calling on him and it was something we were going to have to deal with. We both knew about that possibility going in to this week because we had talked about it. It was a combination of the team's performance and his desire not to focus on his contract right now, which we respect his reasons for. What happens that's not for me to talk about now, he's an Oakland A. He's got a job to do for them. When we get to the offseason we get to the offseason."
It has been an eventful run in Boston for Lester.
In 2006, at the age of 22, Lester was diagnosed with anaplastic large cell lymphoma. Four months later, he called then-manager Terry Francona to tell him he was cancer-free.
Lester was the winning pitcher the night the Red Sox clinched Game 4 of the 2007 World Series in Colorado.
He fired a no-hitter on May 19, 2008, the same season he developed into one of baseball's most reliable left-handed starters.
Aside from a shaky 2012 season, Lester was a model of consistency with the Red Sox, compiling a 110-63 record and a 3.64 ERA while making the All-Star team three times, including this season.
At the time of the trade, Lester was in the midst of one of the best runs of his career. He is 10-7 with a 2.52 ERA in 21 starts.
The Red Sox don't play the Athletics again this season, so it remains to be seen when Lester will next pitch at Fenway Park.