Philadelphia Union are facing a COVID-19 crisis ahead of their Eastern Conference final clash with New York City FC on Sunday.

Several Union players are in health and safety protocols due to COVID-19 and training on Thursday was cancelled.

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"We were able to return to practice today," Union coach Jim Curtin told reporters on Friday. "We hope to have as many players available as possible for our game against NYCFC."

Union were without starters Jamiro Monteiro and Olivier Mbaizo for their playoff win over New York Red Bulls which took them to the semifinals and could be missing even more first-team players for the final.

"Our players have worked tirelessly to get to this point," Curtin added. "I know they'll be brave even in the adversity that we're facing.

"We've stepped up in big moments all year long. Be it international absences, the challenges of CONCACAF, players losing loved ones.

"Adversity on and off the field, this group always finds a way to step up. We will make our fans proud."