Tevez will miss the FA Cup winners' Community Shield clash against Manchester United on Sunday having been granted leave following Argentina's Copa America campaign until Monday.
It was initially thought Tevez would be back at the club's Carrington training base on Thursday but Mancini says the striker had always been allotted 21 days' holiday.
"I have spoken to him, his phone is working again," joked Mancini, referring to reasons he gave for not being able to contact the player earlier in the summer.
"He was happy and told me he would come back on Monday - everything was normal.
"He was on holiday, there was a mistake. We said he needed to come back on August 5 with Zaba [Pablo Zabaleta] but it was my mistake because I told him come back on August 8.
"Carlos comes back on Monday because he has 21 days after the Copa America."
Speculation over Tevez's future has dominated City's summer with the 27-year-old having made clear his desire to leave the club.
Tevez, City's top scorer and talisman last season, has previously said he will never return to Manchester, even on holiday.
A ?40million move back to his former club Corinthians in Brazil collapsed last month and reports have persistently linked him with Inter Milan.
Yet with no new offers Mancini is expecting him back and to play a full role at the Etihad Stadium from next week.
"He doesn't have another team," said Mancini when asked about reports of a swap deal involving Inter right-back Maicon.
"Carlos is a professional player. If he doesn't have another team in the next 10 days or two weeks I think he will play for us and play serious like last year, like always."
When asked whether Tevez was likely to move before the transfer deadline at the end of the month, Mancini added: "I don't know. A lot can happen in one month but if he stays I am happy."
The rumours linking City with Maicon highlight a lack of cover for first-choice right-back Micah Richards.
Because of that Tevez's international team-mate Zabaleta has returned to training and will be available to play at Wembley on Sunday.
Mancini said: "Zaba is here because if we had a problem with Micah we have only one fit right-back."
City's ?38million record summer signing Sergio Aguero, who was also involved in the Copa America with Argentina, will be on the bench this weekend.
The former Atletico Madrid forward has had blistered feet but is now training as normal.
Mancini said: "He is not 100 per cent ready but he is fit to come on the bench."
Mancini could therefore pair ?24million Mario Balotelli with ?27million Edin Dzeko up front against United.
The controversial Balotelli has also made headlines over the summer after clashing with Mancini during City's pre-season tour of north America.
Balotelli was also quoted this week saying he did not like the city of the Manchester.
Mancini said: "He is young, 21 years old and probably missing his family.
"This situation can happen if you want to play in another country, it is normal.
"The problem for Mario is that he is alone. He doesn't have his family here every day. I can understand this, I don't think it is terrible."
The derby element, and City's continuing attempts to eclipse their illustrious neighbours United, has added considerable spice to Sunday's encounter against the Premier League winners.
Mancini is fired up for the game but does not think too much should be read into the result.
He said: "It is the first official match of the season.
"It is important because it is a derby and we want to win, like United.
"But I don't think the teams at the moment are 100 per cent ready to play, like they will be in two months."
Source: Team Talk
Source: Team Talk