San Lorenzo's home match with All Boys in the Argentine first division this weekend has been suspended after Saints defender Jonathan Bottinelli was attacked by a fan of his own club.
Bottinelli was punched by a San Lorenzo fan after Wednesday's practice as he made his way to the dressing rooms, the player told reporters.
"Today we received notice (from the government's security commission) that the match between San Lorenzo and All Boys is not to be played (on Sunday) and we will comply with that decision," the Argentine Football Association (AFA) said on Thursday.
"We've started an investigation to see where our security failed and if we identify those responsible and they are club members there will be exemplary sanctions," San Lorenzo president Carlos Abdo told reporters.
Botinelli said he might quit San Lorenzo.
"As I was going to the dressing room, one (fan) hit me from behind. I know him, but not his name. In the heat of the moment, the first thing that I think of is leaving the club," he told reporters.
All Boys president Roberto Bugallo disagreed with the postponement.
"It think it's the wrong decision because All Boys are not to blame for San Lorenzo's problems," he said.
San Lorenzo, one of Argentina's so-called "Big Five" teams, have been under pressure from fans for their poor results in the Apertura championship where they are in the lower half of the standings with 14 points from 12 matches, including six defeats, 14 points behind leaders Boca Juniors.