Roberto Mancini has accused Samir Nasri of giving only "50%" for Manchester City.
Mancini reckons the £24m Frenchman, who has netted just three times in 24 appearances this season, is half the player he was last term.
"Samir can do better than this year," Mancini said.
"He is a top player, but he has not been playing at his level.
"Samir has fantastic qualities. He should always play well. A player of this quality could be one of the best in Europe. But it's not happening.
"If you are a top player, you know you can improve until the last day of your career.
"But sometimes you get players who think it is not important to work and this is their worst mistake.
"You win the title, you think it's enough to play 50 per cent and you don't arrive the next year."
During an exclusive interview with the Guardian, Mancini confirmed his interest in Napoli's Edinson Cavani and Liverpool's Luis Suarez, as well as Atletico Madrid forward Falcao.
"I like (Cavani) but all the world wants him," Mancini added. "There are big players. I don't know what can happen. "Suarez plays for a top team like Liverpool. Cavani plays for Napoli. There's Falcao but, again, all the managers like him."