And it means that Racing have been awarded a bonus-point 28-0 win that is set to ensure they finish top of Champions Cup Pool A.
An EPCR statement read: "EPCR has been informed by Northampton Saints that they have recorded a number of positive test results for Covid-19 among their tournament squad and as a consequence, the club is not in a position to fulfil its Heineken Champions Cup, Round 4 match against Racing 92 scheduled for tomorrow (Sunday 23 January).
"The Pool A fixture at Paris La Défense Arena is therefore regrettably cancelled with Racing 92 awarded the match on a 28-0, five match points basis, in accordance with the Tournament Rules.
"EPCR would like to acknowledge the efforts of both clubs to fulfil the fixture, and would also like to reiterate that awarding the match to Racing 92 is a tournament management measure with the objective of ensuring that all fixtures in the 2021/22 Heineken Champions Cup are accounted for, and not a sanction."
For Saints, they can now finish no higher than 10th and they could finish 12th - which is bottom of the group - if Bath pick up a point against Leinster on Saturday and Ospreys claim at least a draw at Sale Sharks on Sunday.
Those outcomes appear unlikely though, meaning Saints are probably going to drop into the Challenge Cup knockout stage as that is what happens to the teams that finish ninth to 11th in both pools.
Only the team that finishes 12th will be without European rugby action come the knockout rounds in April.
Saints' 2021/22 Champions Cup pool stage results
Friday, December 10, 2021: Saints 14 Racing 92 45
Friday, December 17, 2021: Ulster 27 Saints 22
Sunday, January 16, 2022: Saints 20 Ulster 24
Sunday, January 23, 2022: Racing 92 28 Saints 0