Thornton’s Fenway Grille, a decades-old sports bar popular with Red Sox crowds, closed abruptly last Monday after 33 years of business.

The restaurant’s owner, Marty Thornton, announced the closure with a social media post on Monday. “After almost 33 years in the Fenway neighborhood, we’re sad to announce that we’ll be closing our doors this afternoon,” he wrote. “Thank you to our neighbors, friends and family for making Thornton’s so special. We love you, Boston.”

The sudden announcement came as a surprise to many Fenway residents, with outpourings of support for the restaurant’s famous 25-cent wings and $5 margaritas. But according to Monty Gold, the building’s landlord, Thornton had been considering closing the restaurant for some time.

“He told me a year ago he wanted to sell, and I think he's had it listed with a restaurant broker for a while,” Gold said. “He actually called me last week to say that he was going to close this week. He’s been with me some 30 odd years. He’s just burnt out.”

At the restaurant, the beige patio chairs were neatly stacked outside. The building was dark, but the outdoor bulbs that line the patio were still lit. A hand written note is taped to the inside of the front door, reading, “Thornton’s has closed their doors. We want to thank everyone for your support over the years.”

Heather Perkins of the Boston Restaurant Group said Thornton had listed the location with the firm about four months prior, and that he had mentioned that he planned to retire. “We’re selling the assets of the business, all the furniture fixtures, the equipment, the leasehold improvements, the licenses, including the full liquor license,” Perkins said. “We have an asking price for just the liquor license for $630,000, and there’s an asking price if they want to purchase the assets of the business without the license at $150,000. It’s a nice opportunity for somebody.”

Perkins said that showings for the location had been ongoing, even before Thornton’s closed its doors last week. “There’s a couple interested parties,” she said. “It’d have to be somewhat of a similar concept [to Thornton’s]. It has to be different than the other restaurants on that block.”

Thornton’s Fenway Grille was the cornerstone of Fenway’s mini restaurant row on Peterborough Street for over three decades. After a devastating four-alarm fire destroyed much of the row in 2009, it was one of the first restaurants to rebuild.

“He’s been doing it since he was a kid,” Gold said of Thornton. “He started out washing dishes, and he’s had all the restaurants, and just burnt out.”

Gold said he would keep the space as a restaurant, in line with the rest of the street.

“It will only be a restaurant,” Gold said. “I wouldn’t put anything else in there.”