Fabricio Coloccini was lucky not to be blinded at Selhurst Park, according to the Newcastle United manager John Carver.
An object, reported to be a coin, was thrown, seemingly from the stands, during Wednesday night's 1-1 draw between Crystal Palace and Newcastle.
The object hit defender Coloccini above his left eye and Carver said his skipper was lucky to not be seriously wounded.
"It just can't happen can it?" Carver said. "It has got to be taken out of the game. What is disappointing from their point of view is that they have an unbelievable crowd here, an unbelievable atmosphere -- it is a fanatical group of supporters in that corner.
"It takes one idiot to throw a coin, I have seen it and it misses Colo's eye by an inch -- another inch and it could blind him."
Pardew said it would be an isolated incident but hopes the club put in the necessary steps to identify the culprit.
"I saw the referee come over to the linesman and hand him something," he said.
"It would be a shame if that was an incident -- a random fan acting poorly if that is the case and that is unusual for this club if that is the case because we have a great record of behaviour so I am sure we will look into it."
Information from the Press Association was used in this report.