Mancini had said that Corinthians had already agreed a deal to sign Tevez before the Brazilian club issued a statement on Monday to deny that was the case.
After the 2-1 friendly victory over Vancouver on Monday, Mancini said: "I slept last night and I had a game to prepare for today so I don't know any more. The clubs are talking."
Asked if he had been in contact with the player, Mancini said: "No, no. I have only one number and it doesn't work at the moment."
Though Corinthians' denial has raised doubts over whether the deal can be resolved before the conclusion of the Brazilian transfer window on Wednesday, it appears City are already resigned to losing their captain as they pursue a deal for Atletico Madrid star Aguero.
Asked when a bid might be lodged for the Argentina forward, Mancini said: "Maybe in the next days. I have not spoken to anyone about it, but probably. I think so."
Midfielder Gareth Barry believes Aguero would be a fine replacement for Tevez and says the players are looking forward to his potential arrival.
"Aguero is a very exciting player from what I have seen on TV," Barry said. "He is a class act. Names like that will excite fans and the players."
He added: "There has obviously been the odd chat about Carlos. He has made it clear he is ready to leave and the players will respect his decision.
"It is down to the club to decide what fee they want for Carlos. We would be sad to lose him because he is a class player who has worked really hard for the club.
"If you believe what you read, then yes, he has played his last game, but he has been great for Manchester City. He has helped the club win its first trophy and he has always given 100%. We are grateful for that."
Goalkeeper Joe Hart also believes Aguero would be a fine signing.
"I watch a bit of Spanish football and the thing about him is he's only ever linked with the top teams," he said. "I've spoken to David Silva about him and he's really given him the nod of approval - that's good enough for me."