How good is Scrabble’s GOAT? He wins in languages he can’t speak.

During the deciding match in November’s Spanish World Scrabble Championship in Granada, Spain, Richards racked up triple-word scores with ENRUGASE (“to wrinkle up") and ENHOTOS (an archaic word for “familiarity"), before clinching victory with TRINIDAD and SABURROSA (an obscure word that describes the coated residue of the tongue).

Not that Richards knew the meaning of any of those words.

One Spanish TV broadcaster called his win the “ultimate humiliation." The global Scrabble community wasn’t so surprised. Richards had done this before—in French.

When he won that language’s Scrabble world championship in 2015 and again in 2018, he could greet his opponents with bonjour but couldn’t say much else.

What Richards lacks in linguistic ability he more than makes up for with an encyclopedic memory and an unrivaled ability to decode patterns, according to friends and opponents.

“He memorizes words as soon as he reads them once," said Hector Klie, who has represented the U.S. in Scrabble since 2003 and competes in Spanish. “He doesn’t know whether a word is a verb, noun, adjective or any other grammatical form that would typically help native speakers learn words more easily. For him, all words are equal in his memory, and he doesn’t need to know their meaning."

Richards is also the undisputed GOAT in English-language Scrabble, having won five world titles. He is currently ranked No. 1 by the World English-language Scrabble Player’s Association.

“We are witnessing someone who could be compared to, or even surpass in intellectual capacity, figures like Bobby Fischer, Garry Kasparov or Magnus Carlsen in chess," said Klie, the Spanish World Championship runner-up in 2004.

The former head of New Zealand’s Scrabble federation, Howard Warner, once described Richards as “a computer with a ginger beard."

Richards cuts a singular figure in the Scrabble world, where he is known simply as Nigel—“a single, universally recognized name like Serena, Rafa, Pelé and Tiger," said Warner. He sports large steel-rimmed glasses, a beard and graying blond hair in a tight bowl cut, giving him the look of an Amish farmer or a stubbled Spock.

Richards, who lives in Malaysia, couldn’t be reached for comment. Friends and rival players say he is notoriously reclusive, though not unfriendly.

Warner characterizes Richards’ personal life as monk-like: A vegetarian who doesn’t drink or smoke, he has no television and little interest in current affairs. In addition to Scrabble, his other interest is cycling, and he often rides hundreds of miles a week.

The New Zealander, who got into Scrabble playing against his mom, is described by friends as a math genius with an encyclopedic memory.

A similar calm pervades his matches—and even his victories. When Richards won his first English-language championship, the MC at the awards ceremony asked him how it felt to be the king of Scrabble. He replied “Nice," took his trophy and walked off stage.

“Nerves and emotions don’t come into his play—win or lose a game, his expression will remain the same," said Liz Fagerlund, a New Zealand Scrabble official and longtime friend.

Growing up in Christchurch, New Zealand, Richards was brilliant at math, according to Fagerlund. He started playing Scrabble with his mother and in his late 20s joined a local Scrabble club, armed with word lists he had put together in a spreadsheet.

“It was apparent very early on at the club that he was going to be a very good player," Fagerlund said.

Richards’ success points to one of the paradoxes of Scrabble: It’s useful to know as many words as possible, but not what they mean. Words become combinations of letters with different mathematical values that can be arranged in a dizzying variety of permutations, which change as a rival player places their words on the board.

Richards poses with Alejandro Terrenzani, who said the player’s win in Granada caused ‘astonishment and admiration.’

Even so, playing the game in another language requires the command not only of a new lexicon but of a different game strategy. In Spanish, it is more common to make a seven-tile move, called a bingo, compared with the English game, which boasts more five-tile moves.

The largest Scrabble tournaments, including players from multiple countries, are the English, French and Spanish language championships, Klie said, though there are local tournaments in other languages.

Richards’ win last year in Granada caused “astonishment and admiration" among Spanish-language Scrabble aficionados, said Alejandro Terrenzani, a member of the Spanish Scrabble Federation.

“Not all his rival players were happy about it, but everyone recognizes his enormous capacity," he said. Richards had to adjust to a distinct methodology, and anticipate his opponent playing in a way that he was unaccustomed to.

The tournament’s runner-up, Benjamín Olaizola, said Richards threw him off his game with unusual tactics. Richards could have used all his letters at one stage. Instead he chose a different word that didn’t give him bonus points but allowed him to score more points later in the game, said the Venezuela native who now lives in Argentina. He called his opponent “the best player in the history of Scrabble."

Some of Richards’ games have become Scrabble lore. During one English-language match last year in India, Richards had the letters A-C-E-N-O-R-T and, given the words already on the board, could have used all of his tiles (for a bonus 50 points) in four different ways—ENACTOR, COPARENT, SORTANCE and SARCONET—scoring between 70 and 89 points.

Instead, he racked up 92 points by using the P in ERUPTION and the word TED to create PERNOCTATED, with the A sitting atop NON to form ANON. The moves sent much of the Scrabble world into varying degrees of ecstasy.

Benjamín Olaizola, the runner-up, said Richards threw him off his game. ‘That is to be expected given Nigel’s exceptional level of play.’

“(P)ERNOCTA(TED) is a dizzying feat not only of anagramming and word knowledge but of spatial relations, visual awareness, imagination, creativity and sangfroid," author Stefan Fatsis, whose book “Word Freak" looked at the world of competitive Scrabble, wrote in Defector. “It is, in its own way, art."

The game also showed how Richards’ forays into other languages has made him an even more formidable opponent. Pernoctate, meaning to spend the night somewhere, isn’t widely used in English, but is far more common in…Spanish.

“We are all wondering what dictionary he will tackle next," said Fagerlund.

Write to Natasha Dangoor at natasha.dangoor@wsj.com