Drop-goals will be decisive in close-run games at this month's World Cup, Super Rugby-winning coach Ewen McKenzie said on Thursday.

McKenzie, who this year guided the Reds to their first southern hemisphere championship title in the professional era, said the impact of the drop-goal at the World Cup should not be underestimated.

"[England's] Rob Andrew knocked the Wallabies out in 1995 using the ploy, while Joel Stransky used it twice for South Africa to win the final that same year," McKenzie wrote in his column in The Sydney Morning Herald.

"[Australia's] Stephen Larkham knocked the Boks out in 1999 with his first and only Test drop-goal, while Jonny Wilkinson won the 2003 tournament for England with his right foot strike.

"It won't be used in high volume, but it will be decisive."

McKenzie said that the northern hemisphere rugby nations have mastered the skill of kicking drop-goals.

"But it's interesting that [All Black] Dan Carter, who has kicked just a few drop-goals in his entire playing career, has been practicing," he said.

"Quade Cooper worked tirelessly on it during the Super Rugby season with the Reds.

"It was no fluke the Reds finished second in the [Super Rugby] competition for drop-goals this season."

The World Cup kicks off on September 9 with New Zealand playing Tonga in Auckland.

AFP