The MLS Is Back tournament was to be played on Sunday in Kissimmee, Florida marking a return to men's football in the United States, following the stoppage because of the coronavirus pandemic.
"Major League Soccer announced that today's D.C. United vs. Toronto FC match has been postponed and will be rescheduled," a league statement read. "MLS will announce details later today for the rescheduled match.
"Under the league's health and safety protocols, clubs are tested the day before each match. The results of yesterday's tests for D.C. United and Toronto FC produced an initial unconfirmed positive COVID-19 case for one player and an inconclusive test for another player.
"Because of the arrival time of the clubs in Orlando, the league's protocol called for retesting both teams this morning and to await the results of those tests prior to playing the match.
"Major League Soccer will continue to prioritize the health and safety of all participants of the MLS is Back Tournament in making these decisions."
The latest cancellation highlights myriad of issues facing the return of football following the withdrawal of FC Dallas due to a high number of positive COVID-19 tests, before Nashville SC followed suit.
Orlando City SC kicked the tournament off with a 2-1 victory over Inter Miami CF on Thursday.