Sergio Aguero's brother has hit out at the "unfair" criticism directed at the Argentina striker following a string of poor results in World Cup qualifying.

The Manchester City star has been the focus of ill-feeling after missing a penalty in Tuesday's 1-0 defeat to Paraguay, a result that leaves Edgardo Bauza's men five points behind leaders Brazil following a run of three matches without a win.

Paraguay and Chile - one and two points adrift respectively - are hot on the heels of fifth-placed Argentina, who visit Brazil next month.

Aguero accepts he has not been at his best and even suggested he may be dropped.

But Gaston del Castillo insists his brother will not voluntarily withdraw himself from international duty.

"Yes, it's true. My brother is having a difficult time, as are other players in the national team," he said. "But I think we have to keep calm right now.

"The penalty he missed is a penalty that you can miss.

"He's excited with the national team. People can say whatever they want.

"He's not going to leave the national team. I think he will continue playing for Argentina.

"It really is unfair. It's tough criticism for any footballer."

Argentina have been without the injured Lionel Messi for the duration of their winless run.