COVID-19 impacted the MLS is Back Tournament again Sunday, with a pair of test results on the eve of kickoff prompting Toronto FC's opening match to be called off.

MLS deputy commissioner Mark Abbott made the announcement just minutes before the scheduled 9 a.m. ET start at ESPN's Wide World of Sports complex in the Orlando area.

The league said a round of pre-game testing Saturday had returned a positive test for a D.C. United player and an inconclusive test for a Toronto player. The positive test is considered unconfirmed until backed up by a second test.

Both players and teams were retested Sunday morning. The match will be rescheduled once results of those tests come back, Abbott said.

The tournament has already lost FC Dallas and Nashville SC due to a rash of positive COVID-19 tests.

"We believe the tournament can still be conducted safely," Abbott told a virtual conference call Sunday morning. "And if at the point we determine it can't, obviously we would make a decision then.

"In the case of Dallas and Nashville, the decision was made that based on the extent of the positive tests in those teams (and) their ability to train, that the more prudent course was to withdraw them.

"But we had established a set of protocols that are working as they were designed, which is to identify players that have had positive tests for COVID-19, to remove and separate them from the team and isolate them. And to continue the process of testing the other players ... We view this (case) as the process working."

It marked the second delay for both Toronto and D.C. United. They were supposed to meet Friday night but the game was pushed back to Sunday due to Toronto's late arrival at the tournament because of the need for additional COVID-19 testing in the wake of a player reporting symptoms.

Under league protocols, players who test positive are isolated while those who test negative "move forward."

Abbott said because Toronto only arrived last Monday, the decision was made to await the results of tests conducted Sunday morning before playing the game.

"When we receive the results of those two complete team retests, we'll be in a position to know when the game could be rescheduled," said Abbott.

The deputy commissioner said the results of Saturday's tests came back late Saturday or early Sunday.

"Obviously it happened over a brief period of time but we were committed to making the right decision," he said.

It added to an already stressful morning for the teams given the unusually early kickoff time — made to avoid the Florida heat. Both Toronto captain Michael Bradley and striker Jozy Altidore had criticized the 9 a.m. start, saying it was not conducive to good football.

Toronto's pre-game meal was scheduled for 5:30 a.m. As it was, the team never left the league hotel — located a five- or 10-minute bus ride from the playing field.

D.C. United players did arrive, leaving soon after.

"To every DC United supporter, our families & friends, I'm sorry you woke up so early to see us play, to then have the match postponed AGAIN," tweeted D.C. goalkeeper Bill Hamid. "Especially after so many people planned originally to watch the game which was meant to play on Friday! Have a beautiful Sunday regardless."

Toronto's next game is Wednesday against the rival Montreal Impact. D.C. United faces New England on Thursday.

There were some surprises in Toronto's planned starting 11 Sunday.

While it fielded the same back five as it had in its last league game March 7, there were four changes further forward. Bradley and Argentine newcomer Pablo Piatti, who both missed the opening two games of the season, were to return from injury.

Tsubasa Endoh and Ako Akinola were also in the starting 11.

Altidore did not make the matchday 23. He was late joining the team after spending the lockdown at his Florida home and had to train on his own while fulfilling quarantine.

Canadian midfielder Jonathan Osorio also was not slated to dress.

Sunday's Sporting Kansas City against Minnesota United game was scheduled to go ahead despite confirmation Friday by Kansas City that one of its players had tested positive.

The tournament is the first action for the league since it suspended play March 12 due to the global pandemic.

This report by The Canadian Press was first published July 12, 2020.