When Anders Frisk, one of world soccer's top referees, began officiating at professional games, he was ready for the torrent of verbal abuse from stadium fans that is de rigeur at any high-level match.
He did not expect, however, the death threats that sparked his shock resignation last weekend, throwing Europe's most popular and lucrative sport into turmoil.
The circumstances surrounding Mr. Frisk's dramatic departure have exposed the lengths to which players, coaches, and fans let their passions push them, and prompted calls for authorities to crack down on growing incivility to avert a referees' strike.
"This nonsense has to stop," says William Gaillard, spokesman for the Union of European Football Associations (UEFA). Referee abuse has been an issue for years, he adds. "But now it has taken a nasty turn."
"The game is just not worth all that," Frisk said on the Swedish football federation's website. "The safety of my family is more important than anything."
The trouble started earlier this month, when Frisk ejected a player from the London club Chelsea during a game against Barcelona in the Champions' League, Europe's top club competition.
Soon after the match, Chelsea coach Jose Mourinho accused Frisk of speaking to the Barcelona coach during half time, insinuating that he had succumbed to pressure. Frisk denies the charge.
Mr. Mourinho's comments apparently encouraged a flood of hate mail from Chelsea fans.
"It's the coaches who whip up the masses and actually make them threaten people with death," said Volker Roth, chairman of UEFAs Referees' Committee. "People like Mourinho are the enemy of football."
Neither man is a stranger to controversy. Frisk, a flamboyant Swede whose blond hair and perma-tan always attract notice, halted a match between AS Roma and Dynamo Kiev last fall when a coin thrown from the stands gashed his head.
Mourinho, a charismatic Portuguese coach who has taken Chelsea to the top of the English football standings, was fined £5,000 ($9,500) last week for an earlier allegation of deliberately unfair refereeing.
Some observers see Mourinho's sniping as standard gamesmanship in the charged atmosphere of multimillion-dollar soccer championships. "Managers use everything to try to gain themselves an advantage," including trying to intimidate referees, says Matt Tench, sports editor at The Independent, a London daily. "That's the way sport is played at the highest level."
Soccer has long stirred fierce passions in many European souls. "There is something very elemental about a football match" says John Carlin, author of "White Angels," a recent book about the star- studded Real Madrid team. "It's your tribe at war with the other tribe."
Referee abuse is on the rise, soccer officials say. They point to the case of Urs Meier, who received 16,000 insulting e-mails last summer, including death threats, after a British tabloid newspaper published his e-mail address. Mr. Meier's "crime"? To have disallowed an England goal against Portugal in the European Championship.
"It is not uncommon for leading referees to receive hate-mail, broken razorblades in envelopes, that sort of thing," says Willie Young, a former international referee who once received an e-mailed death threat.
Mr. Young puts the abuse in the context of what he sees as declining sportsmanship in soccer. "Simulating fouls, feigning injury, deceiving the referee, open protest against decisions - all this has certainly escalated" in recent years, he says.
While he places most of the blame on "a lack of responsibility by players and managers," he also worries about "certain sectors of the media that are more than happy to emphasize differences of opinion because they sell newspapers."
Such differences are easy to chew over at length now that televised football is all over the European airwaves, thanks to lucrative deals between TV stations and soccer authorities. Scores of camera crews cover major games, offering endless angles from which to review controversial decisions in slow-motion replays.
The referee, by contrast, is alone making his split-second judgments, enjoying occasional help from a linesman, but with no recourse to the video replays on which American football referees can rely. And the stakes for each call are high: Millions of dollars in club revenues can depend on a single goal.
"These referees are in a quite impossible position," says Mr. Carlin.
But referees are reporting difficulties even at the lowliest levels of youth soccer, where matches are watched only by spectators on the touch lines. Verbal threats from overenthusiastic soccer dads force more referees out of the game than hate e-mail, says Young, because "the physical presence in public parks is much more threatening."
"At grass-roots level, fewer people want to become referees," UEFA refereeing chief Roth said this week. "Who is going to do that if you are going to be abused?"
UEFA sees "no obvious solution" to the problem, according to Mr. Gaillard. "Whatever we try to do to protect the privacy of referees is going to be extremely difficult," he says. Instead, he suggests, "it is a question of educating players, managers, and fans so they have a different attitude to referees."
He also advocates tougher sanctions against miscreants, pointing out that the $9,500 fine imposed on Mourinho probably meant little to a man who earns millions of dollars a year.
Meanwhile, says Young, most referees will go on refereeing, even for the meager allowance that is their only reward, "because we are football crazy. We wouldn't be involved otherwise. This affair could give people a reality check, but I doubt it."