McCullum is the Federer of cricket - AB de Villiers

AB de Villiers on McCullum: I truly love the way he plays the game. He plays with a lot of passion, pride and energy. It's difficult to do that consistently.

On the eve of Brendon McCullum’s retirement from cricket, former South African batsman AB de Villiers likens the Black Caps captain to tennis great Roger Federer. Writes Charlie Bristow

For years, fans have seen South African cricket captain AB de Villiers as a daring, gallant and even belligerent man, keen to decimate bowling attacks with his slashing bat.

Mention the name Brendon McCullum and the image changes. You see a softer, more jovial man.

Ask him about Baz's retirement and the picture changes again, a more intimate side is revealed.

As preparations for New Zealand's test against Australia in Christchurch ramp up, so do the sentimental words for the Black Caps captain.

Listen: AB de Villiers looks back on the career of Brendon McCullum

Everyone is keen to have their say, add their story, share an anecdote about McCullum and de Villiers is no different.

The pair have been fierce rivals on the field throughout McCullum's 14-year international career, but great friends off it.

One only has to look at last year's Cricket World Cup semifinal, when the Black Caps dramatically beat South Africa.

The dejection de Villiers and his team felt after that match was high, but de Villiers still led his troops into the New Zealand dressing room to share a beer with McCullum and his team.

"One thing I admire the most is the fact that, off the field, he is a fantastic human being, a really good friend of mine and that is something I will always respect." de Villiers said.

"I truly love the way he plays the game. He plays with a lot of passion, pride and energy. It's difficult to do that consistently.

"I can think of someone like a Roger Federer, who's someone else to have achieved that throughout his career.

"Maintaining that consistency, that passion, that pride and energy... Brendon has definitely achieved that."

De Villiers concedes that is perhaps McCullum's shining quality - his love for the game and the vigour in which he plays it.

The South African batting genius has struggled with this aspect, stating earlier this year that he was contemplating his future. He admitted that at times over the past few years he was not enjoying the game as he should.

He says that seemed a different story with the Black Caps captain.

"What makes him a great cricketer is the fact he always plays with energy and passion. That is something I admire because I like to play that way.

"It is really difficult to maintain that throughout one's career. So for him to have done that, for that many years, time and time again, I just admire that so much."

When the Christchurch test concludes, there will no doubt be chatter about McCullum's legacy.

It's easy to quantify in numbers what he has achieved for the Black Caps.

Leading them to their first ODI World Cup final, being the most successful Black Caps captain and only New Zealand Cricketer to score a triple century in an international test match are just a few records McCullum has notched up since taking over as captain in 2012.

What is harder to measure is the impact he's left on cricket as a whole in New Zealand.

De Villiers believes the way he led the Black Caps to the World Cup final is his shining moment.

"The youngsters who looked at that whole display of New Zealand almost winning the World Cup will be encouraged to do so in the future. So his legacy that he leaves behind leaves a good taste in everyone's mouth."