Tom Brady didn't offer a specific reason when he retired from football for the second time earlier this month.

In the days since his announcement, Brady has said one reason he's walking away is because it's the "right time."

In an interview with ESPN's Mike Greenberg, Tom Brady, Sr. revealed a reason why the quarterback decided to call it quits.

"This has been a really rough six months on his personal life, his family life, on his football life," Brady Sr. said of his son. "He once said this, he said, 'I'm getting tired of getting hit.' You know, having played 23 years and he holds the ignominious record of most sacks [taken] in the NFL -- I think 600 or 700 sacks -- and there must be another two or three thousand knockdowns."

With Brady getting older, it seems that the hits were starting to take a bigger toll. 

"At 45 years of age, you say, 'Hey, do I want to get hit one more time,'" Brady Sr. said. "The answer's really 'No, I really don't want to unless everything's clicking.' Unfortunately, it wasn't clicking this year and I think it was a foregone conclusion [that he would retire]."