He said the following in a podcast after his last game. Maybe they decided as a family that he would retire. 

"My wife [Gisele Bundchen] is my biggest supporter,” Brady said on his “Let’s Go!” podcast earlier this week. “It pains her to see me get hit out there, and she deserves what she needs from me as a husband and my kids deserve what they need from me as a dad. I’m gonna spend some time with them and give them what they need, because they’ve really been giving me what I need the last six months — to do what I need to do and I said this a few years ago. It’s what relationships are all about. It’s not always about what I want. It’s about what we want as a family. And I’m gonna spend a lot of time with them and figure out in the future what’s next.”

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