Chianti is a region in Tuscany, not a grape.

It’s also the fact Sam Decker learned about seven years ago, while reading a book on the New York city subway in an effort to prepare himself for an interview at an Italian restaurant.

“I had never waited tables before but I told them I did,” he said. “I couldn’t find a job in what I studied in college at Oberlin — creative writing — but I could speak Italian. I spent a semester abroad in Florence.”

The job interview went well. “He put me on the floor that night,” said Mr. Decker.

But his first shift was also his last. “It was one surreal night of totally faking it, pretending to be an Italian wine expert from information I just read in a book on the subway,” he said. “I guess they were trying out a bunch of people for the job. I didn’t make it.”

At the end of his shift, the bartender poured him a glass of red wine.

“It was a glass of Montepulciano, a very fruit forward wine from Tuscany,” Mr. Decker remembered.

“Every sommelier has their epiphany wine. There was a sense that night that was mine,” he said. “There was some magic in that moment sitting at that bar, having that glass of wine, how fresh it tasted. It brought me back to my time in Florence.”

It also led him to a new career, one that eventually brought him back to the Vineyard, where he was born and raised.

Mr. Decker, 30, is no longer faking it. Currently, he is the sommelier and beverage director at Atria in Edgartown. He is also one of three wine personalities to face off on Oct. 17 at 2 p.m. at the Sommelier Throw Down!, part of the annual Martha’s Vineyard Food and Wine Festival, which runs Oct. 16 to 19. The throw down is sponsored by Ruby Wines.

“There is so much more to wine than what’s in the glass,” Mr. Decker said. “There is the flavor component, the crossroads of history and culture and all these different things that are so important in terms of appreciating it, especially when pairing it with food. That’s what I remember when I drank that glass of wine. That’s what I hope people will learn about wine at the throw down.”

This is the first Food and Wine Festival Mr. Decker is participating in. But pairing food with wine is something he’s familiar with. In 2009 he and his wife Katy vacationed to San Miguel de Allende, Mexico, and eventually decided to move there. They opened a restaurant together called Oko and starting splitting their time between Mexico and Martha’s Vineyard. This is the fifth year the couple has run Oko.

“I learned everything I know about restaurants in a foreign country,” he said. “I never trained.”

But wine is a different story. He has studied wine ever since that glass of Montepulciano in New York, and is currently pursuing a degree in enology from the University of California, Davis. “There is the side of wine that’s grounded in chemistry and microbiology and then there’s the romantic side,” he said. “And they’re both amazing and I love sharing that.”

At the sommelier throw down, Mr. Decker will give guests a taste of what it’s like being a sommelier, by pairing wine with food. In the throw down, he will face off against Joseph Carr, founder of Dylan’s Ghost Winery, and Mark Fine from Vine Connections.

“We each saw the menu and had to select wine pairings from a list of 300,” Mr. Decker said.

Guests pay $60 to participate in the competition. Diners get to eat the four-course meal and choose their favorite wine pairings to select a winner. The three wine experts will get to argue their case for each pairing. Chef Rachel Klein of Liquid Art House in Boston will moderate.

So what’s Mr. Decker’s strategy?

“I picked wines that are off the beaten path,” he said, a strategy that’s worked quite well for him in the past.

The Martha’s Vineyard Food and Wine Festival runs from Oct. 16 through 19 at various locations around the Island. For a complete list of events and to purchase tickets, visit mvfoodandwine.com.