Beauden Barrett, pictured playing against Wales last year, could become the world's best ever first-five.

Beauden Barrett could supplant Dan Carter as the world's best ever first five-eighth, according to Ronan O'Gara.

The former Ireland and Lions No 10 and Crusaders coach said Barrett had the potential to challenge Carter for the unofficial title.

"He fills grounds, he excites people. Everything that is good about rugby, is what Beauden Barrett does," O'Gara said.

PHOTOSPORT Beauden Barrett and the Hurricanes will play the Crusaders on Saturday night.

"He is an exceptional talent, he has probably nearly redefined No 10 play.

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"I think Dan was obviously, and still is probably, the best No 10 in the world over all the decades. But Beauden Barrett is very exciting and potentially going to challenge him for that title."

O'Gara is well placed to judge the respective merits of the pair, having played against Carter and then coached him at Racing Metro.

He knows the Crusaders have their work cut out to curb Barrett when they play the Hurricanes on Saturday night.

​The Crusaders haven't won at the Cake Tin since 2012, and not surprisingly this New Zealand derby promises to be loaded with the sort of rugged behaviour that may have officials squeamishly calling for the TMO to pull out his magnifying glass.

O'Gara advised Mitchell Hunt, who is likely to start at first-five for the Crusaders, to make the most of matching up against Barrett.

"I would say enjoy it," O'Gara said. "It's an opportunity, he knows that he can do it and he's delivered for his team-mates before and they have huge confidence in him.

"So, listen, it's 80 minutes. It's not Mitch Hunt against Beauden Barrett, but it's a chance for him to enjoy it and express himself. That's why as a kid you play rugby."

Hunt is starting because Richie Mo'unga broke his jaw against the Stormers last Saturday.

O'Gara said Mo'unga had accepted he has to be patient following his successful surgery. His job, now, is to concentrate on getting fit so he can come back firing and prove himself to the All Blacks selectors ahead of the three-test series against France in June.

"He's very disappointed at the minute, but even since Saturday night to now there has been a change in attitude," O'Gara added.

"He is very positive, he is a very pleasant kid. The most important thing for us is that it is early in the season, I think Richie will be playing tests for the All Blacks going forward as well so with every cloud there is a silver lining as they say.