Paraguay international Salvador Cabanas is in a critical condition after being shot in the head.
The Club America striker, 29, is being treated in intensive care after the incident in a Mexico City bar.
Mexico City’s attorney general Miguel Angel Mancera told TV station Televisa: “We don’t clearly know the motive behind the injury.
“According to an initial report it was a shot from a firearm with a frontal entry point and without exit.
“The player is conscious but he has a heart problem which they’re trying to stabilise.
“We’re waiting to see what those arrested have to say. It seems that the attack happened in the bathroom of the bar.”
Two suspects were detained although the motive of the attack remains unclear.
Cabanas has scored over 100 goals in the Mexican top flight and this season had so far netted 18 in 24 games for Club America.
In 2007, he was named the South American player of the year by Uruguay’s El Pais newspaper, becoming only the second Mexican-based player to win the award.
Club America president Michel Bauer believes the attack was unprovoked.
“He arrived conscious and responded well to the questions they asked him as he was going into hospital,” he said.
“It’s a key point that can be encouraging, but until further notice we cannot speculate on anything at all.
“They wanted to assault him. I can confirm that that is what his wife has said – that it was an assault. There was no shoot-out nor any quarrel.”
Juan Angel Napout, president of the Paraguayan football association president, confirmed they would send a doctor to Mexico to accompany Cabanas.
“We are praying for him,” Napout said.