Tom Brady's had a long, legendary career in the NFL. However, it cannot last forever. How a career ends can add or take away so much from a legacy. Here's why Brady should hang it up if he wins the Super Bowl again at the end of the 2021 season.#1 Going out on topRetiring when on top is one of the hardest acts for a player to do, but it leaves the legacy untarnished. By going out on top, he avoids suffering a Brett Favre-like ending where he plays too long and leaves on a low.Tom Brady on throws 20+ yards in 2020 (playoffs included):🔸45 completions (1st)🔸1,515 yards (1st)🔸15 TDs (1st) pic.twitter.com/9GxVG2DQDq— PFF (@PFF) May 18, 2021#2 John Elway retired after his second win in a rowTom Brady would match John Elway as the only pair of quarterbacks to retire after back-to-back Super Bowl victories. It could be another 20 years before someone like Patrick Mahomes is able to earn the same accomplishment.Basically, his retirement would add another reason why he is the greatest of all time instead of taking one away by playing past his prime.#3 Kyle Trask will be readyIn case it was missed, Kyle Trask ended up going to the Tampa Bay Buccaneers in the 2021 NFL Draft. He'll learn from Tom Brady, one of the greatest to do it. After the 2021 season, Trask will have sat behind Brady for a full year. He'll be ready to take over and deliver another decade of great football for the Buccaneers in 2022.QB Kyle Trask with a nice downfield completion to his second read. pic.twitter.com/bA31YXknDb— PewterReport (@PewterReport) May 15, 2021#4 Retire with GronkowskiRob Gronkowski is still playing and has no clear plans to retire at the end of the 2021 season. However, as he'll be turning 33 as a tight end with a history of injury issues, it seems quite likely 2021 will be his last season.Tom Brady would be able to retire with one of his guys who has been with him for over a decade across two teams.#5 No final injury for BradyMuch of the conversation surrounding Tom Brady is how healthy he is because of his diet and workouts. That said, his mid-40s body can only take so much punishment.There is nothing stopping someone from delivering a catastrophic hit that affects Tom Brady for the rest of his life. If Tom Brady gets ahead of this, he could avoid something terrible.Alex SmithNeedless to say, his family will be relieved when the words finally come out of Brady's mouth. That said, there could be some part of Brady that wants to go out in a final hit of glory.When will Brady decide the time is right? One can only wait and see.Also Read: How long has Tom Brady been in the NFL?