Steve Stavro, who once owned the Toronto Maple Leafs hockey club and pioneered the "big-box" retail trend with his Knob Hill Farms grocery chain, has died.

He was 78. Reports indicate Stavro died overnight of a heart attack.

Steve Stavro loved all sports, but especially horse racing and hockey. (CBC)

Known as "The Honest Grocer," Stavro built a food empire out of one store, which enabled him to get involved in his other passions – hockey and horse racing.

Stavro's Knob Hill Farms began as a small fruit stand in Toronto. It made big news back in 1962 when it opened a 60,000-square-foot "food terminal" in Toronto, marking an early move to the "big-box" food store that is now commonplace across the country.

The grocery chain eventually grew to 10 stores, including nine in the Toronto area.

However, in August 2000, Stavro announced that the chain was closing down amid increased competition from other big-box stores and reports of deep financial debts.

Longtime involvement in Leafs

Stavro was added to the board of directors of Maple Leaf Gardens in 1981. After a long legal fight, he acquired control of the Toronto Maple Leafs hockey club with the financial support of TD Bank and the Ontario Teachers Pension Plan in 1994, four years after the death of the previous owner, Harold Ballard.

The Toronto Raptors basketball team and the Air Canada Centre sports complex were later added to the Maple Leaf Sports and Entertainment portfolio.

Stavro served as chairman of MLSE until 2003, when he sold his stake in the company to Bell Globemedia.

The Ontario Teachers Pension Plan now owns 58 per cent of MLSE, Bell Globemedia has 15 per cent, TD Capital has 14 per cent, and construction magnate Larry Tanenbaum has the remaining 13 per cent.

Stavro's passing comes as rumours float in the financial world that the Ontario Teachers Pension Plan is now looking to reduce its holdings in MLSE to a minority position.

Bill Watters, the assistant general manager of the Leafs during Stavro's reign, told CBC News Online on Monday morning that the death was a shock.

"I had seen him two weeks ago, he looked very good," said Watters.

"He was such a generous man, a wonderful sportsman, so representative of a person who knew sports and invested his own hard-earned money to perpetuate his love for sport."

Avid horse racing fan

Though Stavro had given up the grocery business and the Leafs, he was still involved in horse racing and stabled a number of mounts in Ocala, Fla., Watters said.

"I can't say enough good about him. What I remember most was his pro-active love for the team and the people who worked for him," Watters said.

"His loyalty to people like Pat Quinn [former Toronto coach] and [former general manager] Cliff Fletcher was second-to-none."

Louis Cauz, managing director of the Canadian Horse Racing Hall of Fame, told CBC News Online that Stavro "was a great breeder of champions."

"He ran horses in France. He ran in the Kentucky Derby and the Belmont Stakes. He had a great career as a breeder and a builder."

Stavro took a young stallion named Cool Victor and made him into one of most profitable breeding horses in the country, Cauz said. He also turned out a long list of competitive runners, many of whom were named for Macedonian heroes and successful battles.

"He won the most important race of the year at Woodbine, the Canadian International, when he upset a great field in 1999 with Thornfield," said Cauz.

He said Stavro would likely be nominated for a place in the racing hall of fame in May.