Appearing on WEEI's The Greg Hill Show on Monday morning, Brady understood Luck's reason for walking away.
"It is his life. Everyone has the right to choose what he wants to do," Brady said. "He had a great career, and he was a great player. Everybody wishes they could be healthy all the time. It is a contact sport, and he's certainly had his fair share of injuries, so guys retire at different times. Some at the end of the season, and I have seen a lot of guys retire before the season gets going and this is just one of those examples."
Brady is going into his 20th season and just turned 42. That longevity sits in juxtaposition to Luck who retired less than a month before his 30th birthday. Brady has been fortunate that besides his ACL tear in 2008 the New England Patriots' quarterback has been healthy for the most part. Luck meanwhile has dealt with a litany of injuries from a lacerated kidney, a shoulder injury that wiped out an entire season and the latest calf/ankle issue.
Brady pointed to his support system to explain how he's been able to play at a high level for so long.
"I think it's everything. There's definitely a physical element," Brady said. "There's definitely an emotional element. I think there is a mental element. Everything in my view really has to come together for you to be the best version of yourself as a player, and it takes a lot of support. It takes a lot of people. You see, certainly, you can see me as an individual doing that. I have the support of my teammates, my coaches, my family, my friends, Alex (Guerrero), my training system. All those things really need to come together in order to continue to achieve.
"It feels great when you have that support because a football season is like a marathon. There's moments where it is very challenging whether it's physically, emotionally, or mentally. ... you need somebody to help you push through the hard parts because it's not all easy. It's a great challenge, but it is very rewarding when you meet the challenge, too."
As for the Colts fans who booed Luck while coming off the field, Brady said the emotions of that moment will pass, and memories of the quarterback will be rosier in Indy.
"I think emotions are just that. They come and go," he said. "In the moment, I try and not make any decisions on emotion. We are emotional beings. They just ebb and flow. That is just part of life in my view."