The five-time Ballon d'Or winner tested positive while on international duty with Portugal on October 13 and was set to make a return this weekend.
But it was revealed on Thursday that Ronaldo had tested positive for a second time, showing no symptoms this time.
The Sun report Juventus have informed UEFA of his condition and expect him to take a test 24 hours before the Barcelona clash.
If the test returns negative, it means he'll be able to return to action on October 28, when Juventus welcome Barcelona to the Allianz Stadium.
Messi spoke to DAZN earlier this week and said he hopes Ronaldo can recover in time so the pair can renew their legendary rivalry.
"The one with Cristiano Ronaldo was and is a special duel, which will remain forever," he said, reflecting on their time together in La Liga. "It lasted many years and it is not easy to maintain certain levels for a long time.
"Our teams were also very demanding: Real Madrid and Barcelona, the two strongest clubs in the world. Competing as equals for so many years is something that will remain forever.
"The duel between me and Cristiano Ronaldo was very good on a personal level and I think people enjoyed it."
When asked about the pair possibly sharing a pitch together once more, the Argentine said: "Obviously when Cristiano played for Real Madrid the games were special, against them they always are, but with Cristiano on the pitch they had a particular meaning. It is now the past, now we look forward to today's challenges.
"Wednesday there could be this challenge. We hope that Cristiano can be there and will soon recover from Covid."
Since Ronaldo departed Real Madrid in 2018, the duo have spoken fondly of one another and explained that their careers are interlinked.
Ronaldo said at the 2019 Champions League draw: "I shared this stage with him (Messi) for 15 years.
"I don't know if it has ever happened before in football - the same two guys in the same stage all the time.
"We have not had dinner together yet, but I hope so in the future."- Football on BT Sport (@btsportfootball) August 29, 2019
"It's great to be a part of the history of football. I am there, and of course, he is as well."
Cristiano Ronaldo speaks on his relationship with Lionel Messi :pray: pic.twitter.com/HbicSaS6NW
"Of course we have a good relationship - we have not had dinner together yet, but I hope so in the future.
"We have that battle, he pushed me and I pushed him as well. It's great to be a part of the history of football. I am there, and of course, he is as well."
Featured Image Credit: Cristiano Ronaldo/Instagram & PA Images
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