New Zealand captain Brendon McCullum on Monday predicted highly-rated Kane Williamson could become the country's greatest batsman.

The 24-year-old right-hander hit a breezy 57 in the co-hosts opening World Cup win over Sri Lanka in Christchurch on Saturday, the latest in a series of impressive knocks which also saw Williamson smash an unbeaten 242 in a Test match against the same opponents in January.

"Kane is a phenomenal talent," said McCullum. "I believe he'll go down as our greatest-ever batter. 

"I don't want to put that added pressure on him, but what we're seeing at the moment is a guy who is incredibly comfortable with his game, who keeps trying to develop his game, keeps learning."

Since making his debut in 2010, Williamson has made more than 3,000 runs in 39 Tests at an average of over 45.

In 66 one-day internationals, his record stands at 2,509 runs, with a best of 145 not out, at an average over 46.

Such is Williamson's growing reputation, he was likely to feature amongst the top picks in the Indian Premier League auction taking place in Bangalore later Monday.

"He works very, very hard. He's an incredible team man and I think we've seen that with some of his innings that he's looking to up the ante for the team rather than chase individual milestones along the way," added McCullum.

"It's scary to think how good he could be in the years to come. I wouldn't change him for anyone in the world at number three. I think he's an outstanding player who's going to make some sizable contributions in this World Cup."

Williamson still has some way to seal his legacy in terms of hard statistics. Former captain Stephen Fleming remains New Zealand's leading run-maker in both Tests and ODIs -- 7,172 and 8,007 respectively.

But McCullum, who is the Black Caps' second-highest Test run-maker, is such a fan he believes Williamson is just as good as Indian superstar number three Virat Kohli.

"Virat is an amazing player. His record is phenomenal already, and he's still such a young guy, and the runs that he scores, I think when he gets hundreds chasing, and he'll win most times," said McCullum of Kohli, who hit his 22nd career ODI century in defending champions India's World Cup-opening win over Pakistan on Sunday.

"I guess I'm more familiar with Kane's game and his impact on our team, which is one of the reasons why I say that I wouldn't change him."