Newcastle legend Alan Shearer has called Alan Pardew's position on Tyneside "untenable" after the manager was fined 100,000 pounds by the club for headbutting Hull's David Meyler in 4-1 win on Saturday.
The FA has confirmed it will look into the incident as FA chairman Greg Dyke told Sky Sports News: "It looks serious and we will investigate."
Pardew, who has six years left to run on an eight-year contract, is facing a significant ban with the referee's report being sent to the FA's disciplinary committee.
Now Shearer, Newcastle's record scorer with 148 goals in 303 appearances, has questioned Pardew's future at the club. "What on earth can Alan Pardew say to his players when they misbehave?" Shearer, who managed Newcastle at the back end of the 2008-09 season when they were relegated to the Championship, told beIN Sport. "I have never seen anything like that before, ever.
"Frankly I wouldn't be surprised, and I don't think anybody will be surprised at all, if Alan Pardew were to resign over this. Even if he doesn't want to resign, the club might be saying to him, 'We might be doing you a favour - you resign rather than us sack you', because that will have to be in his thinking also."
Graeme Souness, in charge at Newcastle form 2004 to 2006, called Pardew's headbutt a "sackable offence". He added: "I've been frustrated and upset by a number of things, but I've never gone down that road. "Pardew has a track record of confronting people - he is extremely passionate, but this passion this time has gone too far."
Pardew apologised for the incident and said he meant the Hull player no harm, but admits he has let himself and the club down after an impressive display from the Magpies.