The epidemic of uncertainty unleashed by the worldwide coronavirus outbreak continued to victimize the sports schedule Thursday, as such cherished annual events as the NCAA Tournament and spring training toppled like dominoes and the fate of others like the Masters, Kentucky Derby, and the NBA and NHL playoffs hung in limbo.

In addition to the cancellation of March Madness and the remainder of baseball’s Florida and Arizona exhibition seasons, the NHL, MLS, and ATP Tennis Tour suspended play.

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The PGA Tour scrapped the rest of the Players Championship and shut down its other tournaments for the next three weeks. The LPGA Tour canceled three golf tournaments, and all NCAA winter and spring championships were eliminated.

NASCAR races will still take place, but without fans, a silent atmosphere that figures to be as eerie as this suddenly empty sports landscape.

The pace of cancellations hit warp speed Thursday, a day after the World Health Organization characterized the illness as a global pandemic. Then, late Wednesday night, the NBA – where two Utah Jazz players tested positive for COVID-19 -- suspended its regular season indefinitely.

By noon Thursday, every major-conference basketball tournament had been canceled. The Big East called its off at halftime of the opening game, a St. John’s-Creighton game being contested in an otherwise empty Madison Square Garden.

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Thursday’s unprecedented actions left scores of unanswered questions in their wake: When play resumes, will leagues alter the length of their seasons? How much revenue will be lost in those cities that were hosting NCAA subregionals and regionals? What will the overall economic impact be on leagues, teams, and athletes?

According to a Temple professor, the paradigms for sports economics might have to be rewritten after this unparalleled health crisis is over.

“This is really uncharted territory,” said Michael Leeds, chair of Temple’s economics department. “During the ’94 baseball strike, one of the things people found was that people who didn’t go to ballgames went to the movies. They had a certain amount they were going to spend on entertainment and they spent it.

“But now there’s nothing to take the place of the sport,” Leeds said. “A lot of movie theaters are closing. Other sporting events and public gatherings aren’t available. Everything is canceled. I think it’s going to alter the pattern of expenditures in a very real way. Netflix, I suspect, will do great.”

Thursday’s most shocking development came from the NCAA, which initially had hoped to salvage its signature basketball tournament by playing the games in empty arenas.

The NCAA is in the midst of a 15-year television deal that will pay it $10.8 billion. Its spring tournament, typically filled with upsets and upstarts, big crowds and bigger ratings, had become one of the sport’s year’s most anticipated happenings. It had been set to debut Tuesday with a pair of play-in games in Dayton.

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"We are fully supportive of the NCAA's decision to cancel this year's NCAA Division I Men's Basketball Championship," read a joint statement from CBS Sports and Turner Sports. "We'll continue to work closely with the NCAA and all of our partners as we prioritize the health and well-being of everyone involved."

How much cities such as Dayton, Spokane, and Tampa that were supposed to host tournament games will suffer economically will depend in large part on their geography, Leeds said.

“If there’s a Super Bowl in Miami in February, people would have been going to a warm-weather city like that anyway,” he said. “Maybe hotels are 90% full instead of 78%. The increment isn’t as big as people think. Even in a city like Spokane, this isn’t going to make or break it.”

Teams, Leeds said, likely have insurance policies that should cover them for unanticipated events like this outbreak. As for lost baseball, basketball, and hockey games, the professor suggested the financial pain cities experience won’t be nearly as great as some imagine.

“Most economists now feel that the impact of a sports team isn’t as big as commonly thought,” Leeds said. “The thought is that a baseball team has about the same economic impact on a city as a mid-sized department store. A football team is much less.”

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How the NCAA and the TV networks handle their financial agreement could impact schools – especially smaller schools – that hoped to qualify for the lucrative tournament. Teams were due to earn $1.68 million for each tournament game they played.

Thursday’s spate of basketball cancellations idled Villanova, which had a 2 p.m. Big East match with DePaul, and Temple, in Fort Worth, Texas, for an AAC Tournament game against SMU.

Meanwhile, the Phillies, Flyers, and Union will be off indefinitely as the COVID-19 postponement parade was joined by Major League Baseball, the NHL, and Major League Soccer.

Baseball, which was counting on completing its Florida and Arizona exhibition season, yielded to the worsening reality Thursday. Not only was spring training shut down, but its owners decided to delay the scheduled March 26 start of the 2020 season by at least two weeks.

Penn State canceled its Blue-White game, which annually concludes spring football practice.

Before announcing its stoppage, the NHL had canceled Thursday’s morning skates and practices and advised the Flyers and the league’s other 30 teams to look for arenas that could host games into July.

“Our goal is to resume play as soon as it is appropriate and prudent,” the league said in a statement, “so that we will be able to complete the season and award the Stanley Cup.”

The NIT, a postseason tourney that takes place in campus arenas until its semifinals shift to Madison Square Garden, is still slated to take place, but without fans.

PGA commissioner Jay Monahan had said earlier Thursday there would be no fans at the TPC Sawgrass for the final three rounds of the Players Championship or at the next three tournaments on the PGA Tour schedule.

The tour changed its mind late Thursday.

“We did everything possible to create a safe environment for our players in order to continue the event through the weekend,” the tour said in a statement. “But at his point — and as the situation continues to rapidly change — the right thing to do for our players and our fans is to pause.”

There was no word whether the Players Championship would be rescheduled.

As of Thursday afternoon, officials of the Masters, one of golf’s four majors, to be played April 9-12 in Augusta, Ga., were still monitoring the rapidly changing crisis.

A club source told Golf Digest that recent developments “have put all options on the table,” including limiting or banning fans. A decision, the source indicated, was likely by early next week.

» READ MORE: NCAA cancels men’s and women’s basketball tournaments due to coronavirus

NASCAR’s race schedule will go on, though the next two at least will be run with no crowds present.

“At this time, NASCAR will hold its race events at Atlanta Motor Speedway and Homestead-Miami Speedway without fans in attendance,” a statement read. “These events will be restricted to competitors, crews, officials and other necessary personnel.”

In Lousiville, where the 146th Kentucky Derby is supposed to be run on May 2, Churchill Downs officials were taking a wait-and-see attitude.

“Churchill Downs’ utmost priority is the safety and health of our guests, team members and participants, and we are taking all necessary steps to ensure a safe and successful Kentucky Derby 146,” the statement said. “We will continue to closely monitor and assess the impact of COVID-19 in the coming weeks, working with and seeking guidance from public health experts and federal, state and local authorities ...”

Professional soccer in the U.S. came to a standstill Thursday as the MLS, the second-tier USL championship, the U.S. Soccer Federation, and the sport’s regional governing body, CONCACAF, all canceling or suspending games.

The MLS will postpone games for at least 30 days. The Union’s home opener had been set for Saturday.

“Our clubs are united in the decision to temporarily suspend our season, “MLS commissioner Don Garber said in a statement, “in the best interest of our fans, players and employees.”

Events on tennis’ ATP Tour and ATP Challenger Tour will be halted for six weeks.

“This is not a decision that was taken lightly,” said ATP chairman Andrea Gaudenzi. “However, we believe this is the responsible action needed at this time.”