At the end of the day, I just think Lucks passion for football wasn't near what the Mannings, Bradys, Rodgers, Brees passion is. He said he "lost his love for the game" and while I do truly think he loved the game, his passion just wasn't there. This is nota knock on Luck at all either. If I had 100 million in the bank, a wife, a kid (which I do minus the money lol) and was constantly being banged up before the age of 30 I would likely retire too. Guys like Tom Brady, Peyton Manning eat and breathe football. Luck is just a bit different. He likes football but it's not his everything. I think he would be just as happy going for a jog around a nice park than winning a Super Bowl.
As mentioned before, this was not a career ending injury, Luck was shown on the field walking perfectly fine.... So it's a mental issue. It might start with Grigson and never giving Luck the protection he needed from his O-line, but it's ending with Luck. To retire at 29 when he is hitting his prime with arguably the most talented team he has been apart of is definitely strange. We will never know the true story behind this, but his passion for the game isn't anywhere near some of the greats otherwise he wouldn't be retiring.