SAN DIEGO — With one magical swing, Bartolo Colon tested the bounds of human comprehension and confirmed, at long last, the existence of a baseball God.

How else to explain the sight of the portly part-time cult hero floating around the bases Saturday night, savoring the end of a 19-year chase for his first major league home run, proving once again that absolutely anything on a baseball field is possible?

“This is probably the biggest moment in my career,” said the former Cy Young Award winner, who pitched the Mets to a 6-3 victory over the Padres.

Of course, what he did in 6 1⁄3 innings on the mound was incidental. As were the other three home runs hit by the Mets, including one by David Wright, who reached base five times.

This was a night to celebrate the absurd beauty of a man with a beer league softball body achieving one of the most difficult individual accomplishments in sports. His last home run had come in the offseason, during the Friday night softball game he’s played in for years with old pals in the Dominican Republic. “It’s one of those things where you come to the ballpark never knowing what you’re going to see,” Wright said. “And you saw it.”

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Before ending one of the most entertaining homerless streaks in baseball history, Colon stepped to the plate for the 247th time, a career .089 hitter with two extra-base hits on his ledger. Three pitches later, Padres righthander James Shields became a footnote to history, watching Colon round the bases on his second-inning two-run shot.

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In the dugout, manager Terry Collins doubted his own senses. He needed a moment to process it all. “Oh, my God,” he thought. “He hit a home run.”

Until Saturday night, Colon’s at-bats were the stuff of animated GIFs that filled the Internet. His helmet-dislodging pretzel-twists made for perfect fodder. But he has flashed power in batting practice, such as the time he triggered a Twitter firestorm one quiet morning in spring training, when one of his homers took out a distant tree branch. “We all had a hunch that if he were to run into one, it was going to go,” Kevin Plawecki said.

Plawecki was at second when Shields tossed a get-me-over 90-mph meatball over the heart of the plate. Colon tightened the grip on his 28-ounce bat, coiled his hulking body and uncorked a quick swing. “Any time I see a fastball, I swing hard because I’m not a curveball hitter,” he said, disbelief coloring his words. “Once I hit it, I knew it was gone.”

The bat barrel met the ball, and for an instant, Colon staggered off balance. From the batter’s box, he tracked the flight of the ball, near a “hit it here” target just beyond the fence in leftfield. The drive carried, and carried, and carried. As Colon approached first base — the bat still in his hands — history disappeared over the fence. And it was no cheapie. According to Statcast, the ball came off Colon’s bat at 97 mph and traveled 365 feet.

“I almost missed third base, I was so excited,” Plawecki said. “I was just kind of in awe about the whole thing.”

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Colon is beloved in the Mets’ clubhouse because he is a living, breathing reminder that baseball ought to be fun. And he again inspired that kind of joy. In the dugout, his teammates jumped up and down, moved by their sheer disbelief. As a smiling Colon rounded third, he noticed the dugout suddenly was empty. Like mischievous boys, his teammates had scurried into the tunnel leading to the clubhouse.

At 42, Colon became the oldest player in baseball history to hit his first home run. And now he would receive the silent treatment, no different from a rookie.

“We all know he’s an entertaining guy at home plate,” Collins said. “So to have him ambush something like that and hit a homer, it’s pretty special.”

If the Kentucky Derby is the most exciting two minutes in sports, the most exciting two hours might be a Colon home run trot. He made Kirk Gibson on a bad leg look like Usain Bolt in the 100. Statcast measured his journey at 30.6 seconds, but it seemed to take much longer. Nobody paid any mind, though. He had waited nearly 20 years for this and had earned the right to savor it.

“My heart was beating a lot,” Colon said. “Today is a day that I’m never going to forget.”

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Yoenis Cespedes hit a two-run homer and Wright and Michael Conforto added back-to-back solo shots in the ninth. But Colon’s blast stole the spotlight.

Only three Mets have homered at age 42 or older: Willie Mays, Julio Franco and now, the incomparable Bartolo Colon.

“This is one of the great moments in the history of baseball!” Gary Cohen boomed on the team’s TV broadcast. “Bartolo Colon has gone deep!”