Players felt the full force of the International Rugby Board's (IRB) new 'zero tolerance' policy with a glut of yellow cards and one sending-off during yesterday's 36 pool matches.
Steve Griffiths, the IRB's referees' manager, believes the crackdown, in which first offences result in an immediate two-minute sin-bin, is keeping the players check.
However, the first yellow card to be dished out yesterday, to Hong Kong's Rowan Varty during his team's opening match against Canada, was a case of mistaken identity. Varty's yellow card was later erased from the record.
'Standards of behaviour are quite high,' said Griffiths. 'If the players can maintain these standards throughout the next two days, it will turn out to be a great tournament.'
The first four games had four sin-binnings and as the day progressed a steady stream of players spent time on the sidelines. But Griffiths said overall behaviour had improved. 'We want to avoid the mass brawls in the past that have marred the IRB sevens tournaments,' said Griffiths.
He said that last year there were two brawls in a tournament in Chile and one in Uruguay.
There was one red card yesterday, with Uruguay's Nicolas Brignoni banished from the field for good after his second yellow card in the same match, against South Africa.
Brignoni was later banned for one match by the tournament disciplinary panel and was forced to sit out Uruguay's game against Tunisia.
The IRB's zero tolerance policy is being strictly adhered to by referees, who have been told to clamp down on high tackles, shirt-pulling, tackling without the ball and other on-field offences.
'We have a group of referees who have been together for two years and they know what they have to do,' said Griffiths.
Tournament director Mark Egan said the IRB's firm stance on discipline was going down well with teams and players. 'Everyone has accepted it,' he said. 'We have had no complaints from anyone.'