Saturday’s two Women’s Super League fixtures have been postponed because of positive coronavirus tests.
Arsenal’s game at Aston Villa and Manchester City’s clash with West Ham United have both been called off.
The Gunners requested a postponement after a player tested positive for Covid-19 on her return from an unsanctioned trip to Dubai.
City reported four players, who had also visited the United Arab Emirates, had tested positive earlier this week.
New dates for the two matches are yet to be announced.
BBC Sport understands Manchester City, who are fourth in the table, have also suffered a number of injuries in the squad, as well as losing United States duo Rose Lavelle and Sam Mewis to international duty.
One player is self-isolating after coming into contact with a household member who tested positive for coronavirus. This is in addition to the four players who returned positive results in the latest round of testing.
West Ham, in 10th, are believed to be understanding of the situation having had to postpone their game with Villa last month because of “a small number” of positive Covid-19 cases at the club’s training ground.
Saturday’s match was scheduled to be the first in charge for new West Ham manager Olli Harder, who agreed a two-and-a-half-year contract last month.
Second-placed Arsenal confirmed in a statement that all their players initially tested negative on their return from the Christmas break.
“One player has subsequently tested positive for Covid-19 this week,” it said.
“As a result, several first team players are now observing a period of self-isolation as a precaution in accordance with FA and UK government protocols.”
In a statement, the Football Association said both City and Arsenal had shown they would be unable to name a minimum of 14 players for their fixtures.
“With the health of players and staff the priority, the FA has decided that these matches will now be rescheduled,” the statement said. “We wish those with Covid-19 a safe and speedy recovery.”