The trouble flared among the 18,000 crowd after Emile Heskey had a shot saved during Leicester's 3-1 defeat by Olympiakos in Athens, in which Leicester's promising midfielder Stuart Campbell scored their goal.
O'Neill and his staff had to run for cover as bottles and coins showered on to the bench, and O'Neill considered calling off the match. "I was serious about calling off the game there and then," he said.
In the dying seconds of Monday's contest the Leicester players had to flee after the home fans ran on to the pitch.
The former England goalkeeper Peter Shilton has joined Middlesbrough as a specialist goalkeeping coach.
Shilton will work in a part-time capacity in succession to Mike Kelly, who recently joined Nottingham Forest.
Middlesbrough's manager, Bryan Robson, said: "I cannot think of anyone better than Shilton to take over from Kelly."
The 12-year-old son of Diego Maradona has signed as a junior for Napoli, the side his father steered to two Italian league titles, club officials said yesterday.
Napoli said Diego Armando Jnr, who has been legally recognised as Maradona's son by an Italian court although the Argentinian has always maintained the boy is not his, was taken to the club by his mother Cristiana Sinagra.
The boy will begin training with one of Napoli's junior squads next season.
Maradona was ordered in 1992 to pay maintenance of around 5million lire (pounds 1,800) a month to his former lover, Sinagra. In 1995, he appealed against the original court order but lost.