The game against Bordeaux-Begles was to be the first competitive match for the Scarlets since October.
Rugby matches between French and British teams were to be played this weekend, but have been postponed because of France's new travel rules.
Bath and Sale will not play in the European Cup on Saturday, as will the Challenge Cup match between Biarritz and Worcester.
All of the rugby games on Sunday are off.
The games can be played later in the tournament.
Travelers who are not French residents or citizens will need to provide a negative Covid test less than 24 hours old and be isolated for at least two days from Saturday.
There were insufficient assurances that the matches would not be at risk after the board received briefings from the professional leagues.
As soon as possible, EPCR will provide a further update.
Racing 92 was awarded a 28-0 bonus-point win because of the coronaviruses cases in the Welsh camp, and the game was called off.
The game between Montpellier and Leinster was called off because of the Covid cases.
The Challenge Cup game between Pau and Saracens was canceled.
The analysis was done.
Chris Jones is a rugby union correspondent.
The third season of the tournament has been compromised, with the latest round of postponements throwing the tournament into a further state of uncertainty.
The seven games that were called off this weekend will be re-arranged by the EPCR.
With spare weekends in the calendar at a premium, the obvious solution is to scrap the home-and-away last-16 matches in April and have a straight one-leg knock-out, freeing up one weekend to clear the backlog but denying fans an exciting new format.
The Scarlets were forced to give up their match with Bristol after falling foul of the rules on returning from South Africa, while Covid outbreak at Leinster and the Ospreys meant they were also hit with 28-0 defeats this week.
Friday, 17 December: Northampton vs. Ulster.
Saturday, December 18th, is the day of the rugby match between Quins and Wales.
Glasgow v Exeter is on Saturday, December 18.
Saturday, December 18th: Castres vs. Munster.
Sunday, 19 December: Connacht vs.Leicester.
The remaining round two of the Challenge Cup.
Friday, 17 December: Dragons play Lyon.
Friday, 17 December: Zebre vs. Toulon.
The Gloucester v Benetton game is on Friday, December 17th.
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