Former club captain Tevez has been frozen out since Roberto Mancini accused him of refusing to play in the Champions League clash with Bayern Munich in September, although he was later charged with the lesser offence of refusing to warm-up in a club disciplinary hearing.
Mancini has told Tevez he can play again for the club if he apologises for his actions, but the 27-year-old has remained silent and appears set to seek a move away from Manchester in January.
"What happened is very sad," Aguero said on ESPNDeportes.com. "Carlitos is now training at the club, but not with us.
"It is a shame. Hopefully, in these days or the next month it can be solved and he will be with us."
Midfielder Yaya Toure has hailed City's "amazing" squad following their flying start to the season.
Despite the disruption caused by the Tevez issue, City are five points clear at the top of the Barclays Premier League table and are well-placed to progress out of the group stage in their debut Champions League campaign.
Toure has played a vital part in City's impressive start and, after scoring a double in last week's European success at Villarreal, the Ivorian scored the winner at QPR on Saturday.
The 28-year-old will, however, miss a key part of City's season in the new year when he is due to play for the Ivory Coast at the African Nations Cup.
Toure is sure his presence will not be missed though because of the wealth of talent at Eastlands.
"I don't think so because we have a lot of fantastic players," he said.
"The squad now is amazing. Everybody is fit now and trying to play at 100%.
"Gareth Barry and Nigel de Jong are fantastic players, James Milner can play in midfield, Samir Nasri can too.
"We have a fantastic squad and I am very happy for that. I don't think it will be a big problem."