Ben Rothman is the champion of the world, and practically no one knows it.

“Never heard of him,” said Lynda Hungerford, who was walking her dog near the shore of Lake Merritt in Oakland, only a few feet from where the champion of the world was practicing the thing that he is world champion of.

Rothman smiled. It’s OK, he said. It goes with being the world champion of golf croquet.

“This is what you call a niche sport,” he said. “Nothing I can do about that. It’s not something to get into if you’re interested in living in lavish luxury.”

Golf croquet is a variation of the tea-and-crumpets variety of croquet. Rothman became champion by winning a big tournament two months ago in England, a place where croquet is tolerated somewhat more than it is here in the colonies.

As with regular croquet, you have to wear white pants for the formal matches. But it’s one shot per turn with everyone vying for the same hoop at the same time, and the play goes faster.

Even two months after becoming world champion and getting a shiny trophy from the World Croquet Federation, when Rothman wanted to play croquet on the court by Lake Merritt, he had to join with the rest of the three dozen club members and first clean up the goose poop.

Rothman’s upset, come-from-behind victory is still the talk of the excessively compact croquet world. The other afternoon in Oakland, Rothman arranged the blue, black, red and yellow balls just as they lay two months ago at the key moment in the fifth and deciding game of the championship round, when he was trailing 6-5 and all seemed lost.

His opponent, the highly ranked Mohamed Karem of Egypt, tried to whack Rothman’s ball out of position from a distance of 36 feet. He missed, by a few millimeters. Rothman made the next two hoops and won the title.

“If what he was trying to do had worked, it would have been brilliant,” Rothman said. “It was not an unreasonable attempt. He’s a great player.”

Croquet players don’t trash talk about one another. Their universe is a little too small for that.

After reliving that glorious moment, Rothman and a few pals met for a pickup game. Rothman whacks his croquet balls with a $500 maple mallet inlaid with brass and made by a custom croquet mallet maker in Palm Springs. It’s got his name carved into the 9-inch-long mallet head, as befits greatness.

When Rothman uses it to hit croquet balls, he looks like the pendulum of a grandfather clock. Whacking a croquet ball is done with the arms, not the wrists. The mallet swings between your spread legs. As in golf and in most other activities on planet Earth, the idea is to keep your head centered and to follow through.

Knocking your opponent’s ball out of the way — always the most satisfying part of a croquet game — is crucial to success, the champ said. So is anticipating what the situation will look like a dozen whacks into the future. In that respect, high-level croquet is a mix of outdoor chess and pocket billiards.

Rothman, a software engineer, was born in Berkeley, which, like his hometown of Oakland, is hardly a croquet hotbed. In college he studied psychology, which can come in handy when taking measure of your foe. Years ago he was a croquet pro at a country club near Palm Springs until it became clear that the ranks of paying customers seeking croquet lessons were limited.

The thing about croquet, Rothman said, is that even at the highest levels it remains a work in progress. For the championship tournament, Rothman was obliged to pay his own way to the match a hemisphere away and to pay his own match entry fee of 100 pounds sterling (about $130). That ate into his funds for hotels, so the future world champion slept in a spare room at a friend’s house an hour’s drive from the tournament site.

For his victory, he got no prize money. The zillion-dollar commercial endorsements seem not to have materialized either.

So it was that the life of a world champion was reduced to pickup games with two pals and a Chronicle reporter. Rothman would have clobbered his two pals in the pickup game, but because his partner was the reporter, he didn’t. The game ended in a 5-5 tie because Rothman had to dash off to pick up his kid from child care.

“They don’t like it when you’re late,” the champion of the world said.

Being world champion of croquet instead of, say, basketball does have its advantages, he said. If he were Steph Curry playing a pickup basketball game instead of Ben Rothman playing a pickup croquet game, he would have been mobbed.

“It’s very nice to be able to go to the grocery store or a concert without having to sign things and hand out pictures,” he said. “It’s very nice not having anybody know who you are.”

And nobody did. At Lake Merritt, the parade of passersby who had no idea they were in the presence of greatness continued.

“Croquet doesn’t do anything for me,” said Alex Pineda, who was walking by the croquet grounds with his greyhound, Dominic, for whom croquet did nothing either. “I think it’s cool that he’s world champion. Thanks for telling me. I still don’t care about croquet.”

Steve Rubenstein is a San Francisco Chronicle staff writer. Email: srubenstein@sfchronicle.com