If Rugby World Cup coaches lie awake in the darkest watches of the night, amid a turmoil of bedclothes, it might be because of a single nagging fear which presses on their restive minds.

These aren't the anxieties which make most people wakeful — intangible concerns about an important matter overlooked or a vital task left undone.

In general, Rugby World Cup coaches rest easy that their campaigns are the result of meticulous planning over a number of years in which nothing has been left undone. They have been able to choose the 31 best available players their countries can provide to take on the task of winning the title: they have at their disposal vast amounts of data and analysis on the strengths and weaknesses of prospective opponents.

Yet, still they stir and their slumbers are disturbed by the echo of shrill whistles and by flashing colors, red and yellow.

Their own planning has left nothing to chance but a major factor outside their control — refereeing — troubled coaches before the tournament began, and has grown in magnitude through the first two weeks.

As the World Cup approached there were fears of the potential effect on the tournament of the hard line officiating which has become the norm in international rugby. High tackles or even accidental contact with the head has been been treated with zero tolerance.

Many commentators and some coaches worried that if referees applied the same standard throughout the World Cup the tournament might see an unprecedented flurry of red and yellow cards. Yet in the initial group-stage matches it seemed referees were taking an unusually light hand as a number of incidents which would typically result in censure went unpunished.

The tackle by Wallabies winger Reece Hodge on Fiji flanker Peceli Yato, which later resulted in Hodge being suspended for three games, was at first not deemed actionable by the match officials.

France backrower Louis Picamoles was offside when he claimed a vital intercept in his team's important pool match against Argentina.

The brilliant opening match between South Africa and New Zealand saw a number of incidents which did not result in any sanction. All Blacks captain Kieran Read and prop Joe Moody both made high challenges on Springbok players, and South Africa winger Makazoli Mapimpi seemed to get away with a brazen professional foul.

Irish prop Tadhg Furlong wasn't penalized over a ruck incident which resulted in Scotland flanker Hamish Watson sustaining a tournament-ending knee injury. In several cases there seemed to be a breakdown in communication between on-field and television match officials.

World Rugby appeared to share the view of many that refereeing in the first week was "not consistently of the standards set by World Rugby and themselves."

"Elite match officials are required to make decisions in complex, high-pressure situations and there have been initial challenges with the use of technology and team communication which have impacted decision-making," World Rugby said in a statement. "These are already being addressed by the team of 23 match officials to enhance consistency."

The result has been a sharp spike in the number of players receiving cards or being subsequently cited. Four players — Hodge, Samoa's Rey Lee-Lo and Motu Matu'u and the U.S. forward John Quill — have received three week bans for high tackles.

Coaches are still not happy. Ireland coach Joe Schmidt said he might complain to World Rugby about the refereeing in his team's shock loss to Japan.

"I certainly understand the frustrations of some of the players and in discussing things with them, based on what I saw on the monitor, it's not too dissimilar from the last time we had this referee," Schmidt said.

Wallabies coach Michael Cheika said he was "embarrassed" by the penalty awarded against his center, Samu Kerevi, for a fend as he ran into a tackler in Australia's loss to Wales. Cheika feared referees had been "spooked" by the World Rugby statement.

"Everybody seems worried," he said. "They are all worried about stuff so much.

"I am not sure why they are worried, the players aren't worried. Then it's affecting everything else on the field."

All Blacks assistant Ian Foster said coaches were worried about the potential "double whammy" of a card and suspension for any player deemed to have made an illegal tackle. He said with squads restricted to 31 players, those decisions could affect a team's chance of progressing to the knockout rounds.

The group stage isn't quite halfway through a 40-game schedule, then the knockouts start with quarterfinals.

"That's the double whammy that gets you so we're not only seeing more cards, we're also seeing longer suspensions," Foster said. "That's probably the thing that will have the biggest impact on the tournament."

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