Former Queens Park Rangers goalkeeper Simon Royce believes a player could be seriously injured on the pitch by hooligans in future.
Royce made his comments after Sheffield Wednesday shot-stopper Chris Kirkland was attacked by a Leeds fan at Hillsborough on Friday night.
The Brentford goalkeeping coach suffered a similar incident in 2005 when he was assaulted by a Stoke supporter.
And the 41-year-old reckons the threat needs to be taken seriously or there could be an incident similar to that concerning Monica Seles in 1993, when the tennis player was stabbed during a match in Hamburg.
Royce claims supporters have to realise the pitch is out of bounds, and insists anyone who breaks the rule should be punished heavily.
"The pitch is for the footballers. That is where the football is played," Royce said. "They come to pay to watch, so watch it from the stand where you pay to sit. They need to stay there.
"You go back to the Monica Seles one. It affected her - obviously she was stabbed. But one of these days that could happen to a player.
"The lad who attacked me, I believe he got a three-month jail sentence. I think that was lenient.
"With this one I think it should be for a little bit longer than that and banned from every football ground in the country."