Commissioner Bud Selig did the right thing.

If the reward for a perfect game is supposed to be baseball immortality, Tigers pitcher Armando Galarraga is well on his way.

Officially, there have been 20 perfect games in the history of baseball, including two just last month. Yet other than Don Larsen’s flawless 1956 World Series performance, most people would need a copy of the record book to name even one.

But Selig’s decision not to add the one thrown Wednesday night in Detroit by a 28-year-old right-hander who’s had to scrap for everything guarantees it will live on forever.

The reason most people will remember it is because of umpire Jim Joyce’s blown call on what should have been the 27th and final out of the ballgame — and the injustice done to Galarraga. What they should remember instead is the sweet smile Galarraga flashed in the moment afterward, and how he went back to work without further drama and got the next batter.

That’s what made the game perfect — not the proclamation by Michigan Gov. Jennifer Granholm a day later, not the congressional resolution threatened by U.S. Rep John Dingell calling on MLB to overturn the call, nor even Selig’s decision had it gone the other way.

Everybody make mistakes, and Joyce tearfully owned up to his as soon as he had the chance. He then sought out Galarraga and apologized as best he could, a gesture the much-traveled Venezuelan pitcher accepted with remarkable grace.

“We’re human, we go make a mistake, nobody is perfect,” he said. “In that situation everybody is focused to do their best thing.”

Galarraga knows something about that. He was a hotshot prospect a dozen years ago, signing with the Montreal Expos in 1998, when he was just 16. But it took him five years just to crack rookie ball, and he was little more than an afterthought in two other organizations for nearly a half-dozen years after that.

Galarraga landed with the Rangers in 2007 as a throw-in in the deal that sent Alfonso Soriano to the Nationals. He appeared in three games the entire year and failed to last five innings in his only start. The Tigers weren’t crazy about acquiring him the following year, either, because all they gave Texas in return was a minor leaguer named Michael Hernandez.

Yet Detroit manager Jim Leyland and his new teammates saw something in Galarraga the rest of us are just learning. They liked the kid’s rock-steady temperament, the way he didn’t sweat the small stuff. He rewarded them with a 13-7 season in 2008, good enough to contend for rookie of the year. And even when he slipped to 6-10 last season, the Tigers knew better than to give up on Galarraga.

That’s the lesson in every blown call, whether it happens in the biggest game of the season or a diamond around the corner — what’s important is how an athlete responds to a bad break.

No one wants to hear that because it’s another small crack in the very foundation of sports — that the playing field is always going to be level.

Selig’s decision honored that reality, rather than providing the storybook ending so many people wanted. It doesn’t matter that rewriting the rule books would have been easy as the blown call came on what should have been the last out.

Because it’s also an instance where good precedent would have made bad law. Had Selig changed the outcome, it would have encouraged those still seething over umpire Don Denkinger’s blown call in Game 6 of the 1985 World Series and Rich Garcia’s gaffe in Game 1 of the 1996 ALCS to keep right on raging. Instead, as Galarraga has proved his entire career, what matters most is to keep moving forward.

In his statement, the commissioner hinted that baseball would do the same, beginning with a re-examination of the expanded use of instant replay, among other things, to make what’s become an increasingly tough job — umpiring — a little more manageable. Too bad.

Baseball games are already too long, and there’s way too many played each season to make more than a handful memorable.

But no one will forget this one.

At the very moment Galarraga had perfection stolen from his grasp, he had the grace to remind the rest of us “to do their best thing” every time the chance comes along.