Australian Olympic team chief Anna Meares said the cases were confined to the water polo team
Manchester City return to action following the World Cup break with a League Cup quarterfinal at home to trophy holders Liverpool on Thursday.
The last encounter between the Premier League rivals in October led to several unsavoury incidents on and off the field.
Leading figures have since tried to dampen down the tensions that have surfaced in recent seasons when both clubs have been vying to be crowned champions of England.
Guardiola, asked if he had a message for the fans, also told a pre-match press conference on Wednesday: "Be supporters and support your team unconditionally in the good moments and bad moments."
City had 16 players away at the World Cup.
Ilkay Gundogan and Kevin De Bruyne played in a friendly against Girona last week but Rodri, Aymeric Laporte, Nathan Ake and Manuel Akanji have only been back in training a few days.
Those involved with England and Portugal, along with goalkeeper Ederson, were due to report back later, while Alvarez will not return to action until next week.
Erling Haaland, Riyad Mahrez, Sergio Gomez and Cole Palmer were not involved in the showpiece tournament.
"Step by step people come back. We are happy they are back, in general they played really well," Guardiola said.
"I have a feeling that the players in the World Cup are in a better condition than the players who were here. Sergio, Erling, Riyad, Cole, they missed a little bit.
"Tomorrow is important for players not at the World Cup to regain the rhythm."
Australian Olympic team chief Anna Meares said the cases were confined to the water polo team
The 54-hole tournament will be playing for its usual $25m purse, with $20m allocated to the Individual Event and $5m to the Team Event at the Staffordshire course
India's Jeev Milkha Singh says Carnoustie is ‘the toughest links course of them all’
The game involves both advanced technology as well as live action in a stadium atmosphere in Palm Beach Florida
LIV Golf returns to the UK at JCB Golf and Country Club in Uttoxeter, England
The American rapper will carry the torch through the streets of Saint-Denis, the underprivileged northern Paris suburb that is home to the Stade de France Olympic Stadium
Close contacts of the athlete were being monitored and tested, but the whole team would train as planned
In Julian Alvarez, who won the 2022 World Cup and the recent Copa America, the tournament has one of the highest-profile players