Five years later, it’s still tough to grasp the magnitude of Madison Bumgarner.

It can’t be stated enough what the Giants’ lefty did Oct. 29, 2014, five years ago Tuesday. He ensured Bruce Bochy would go to the Hall of Fame, advanced his own and Buster Posey’s Hall of Fame candidacies, put a lot more money in owners’ bank accounts and accelerated the bragging rights of fans whose team secured its third World Series title in five years.

No one since has come close to Bumgarner’s World Series performance. In fact, few in history have flirted with those numbers. A reminder: In 21 innings, he surrendered one run (0.43 ERA) while striking out 17 and walking one, winning both his starts (including a Game 5 shutout) and earning the Game 7 save.

Those five relief innings in the finale set Bumgarner apart from other World Series legends and capped a postseason in which he threw 52 ⅔ innings, the most in history.

He now might be on the verge of leaving because he’ll be a free agent and the Giants have so many areas of concern and reasons they won’t reach the playoffs in the near future.

Teams have a five-day exclusive window after the World Series to negotiate with their free agents, after which teams must decide whether to give them one-year qualifying offers worth roughly $18 million.

The Giants will do that with Bumgarner, who won’t accept it. We said here they should use the money saved in the Mark Melancon trade on Bumgarner, and perhaps he’d settle for Clayton Kershaw money (three years, $93 million), but more likely he’d pursue Patrick Corbin money (six years, $140 million).

However it goes, Bumgarner will have plenty of suitors, and it makes perfect sense for the Braves to be included, with their young core and a rotation that could use his track record and leadership. That Atlanta is the closest team to his North Carolina roots makes it more feasible.

If he’s a Giant or Brave or something else, make no mistake: Bumgarner will be remembered for his postseason glory, especially when he was at his absolute best five years ago.

John Shea is The San Francisco Chronicle’s national baseball writer. Email: jshea@sfchronicle.com Twitter: @JohnSheaHey