MLS and the MLS Players Association are currently in negotiations about a protocol for players to opt out of the remainder of the season due to the coronavirus pandemic, multiple sources have told ESPN.

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The agreement is expected to be finalized by the end of the week.

A separate protocol had been in place for the just-concluded MLS is Back Tournament, which was held at the ESPN Wide World of Sports Complex in Kissimmee, Florida. The regular season is set to resume in home markets on Wednesday when FC Dallas hosts Nashville SC.

According to one source with knowledge of the discussions, the situations for which the protocol would make allowances include players who have an underlying medical condition or live with a family member who has such a condition. It is not clear what the salary implications would be for players who exercised the opt-out clause.

Another source with knowledge of the situation said that the agreement is expected to take the form of a side letter similar to what was negotiated for MLS is Back. The two sides reached a deal on a new collective bargaining agreement prior to the start of that competition.

While the tournament was ultimately successful, some players did decide not to participate. LAFC forward Carlos Vela -- the league's reigning MVP -- was the most high-profile player to opt out, saying he made the decision so he could remain with his wife, who is pregnant, as well as their 3-year-old son.

Three members of the Vancouver Whitecaps -- forwards Lucas Cavallini, Fredy Montero, and Tosaint Ricketts -- also pulled out of the tournament because of COVID-19 concerns. A fourth, midfielder Andy Rose, didn't travel, as his wife was about to give birth. Real Salt Lake defender Nedum Onuoha also declined to take part.