5 Things: McCullum's heroics, India's continued success and bowlers' balance

Here are five things we learned from Saturday at the 2015 Cricket World Cup:

1. McCullum ... that is all

Brendon McCullum might not look intimidating at 5-foot-7, but he's the same height as Bruce Lee. New Zealand's big boss is approaching his own level of kung fu mastery with his tactical precision on the pitch.

Rather than let an innings meander along to the 50th over from a position of strength as many captains do, McCullum continues to unleash his bowling attack with fists of fury to pummel the opposition's middle order and tail into submission. At the opposite end, Australia's bowlers may be tall and quick and, in the case of Mitchell Johnson, they tried their best to strike painful blows to McCullum's arm at 90 mph. Yet, McCullum carried on without flinching and buzzed around them like a green hornet, stinging bowlers back with a dizzying array of fours and sixes to help spark the Kiwis' dramatic victory. Bow down to BMac or bow out.

Bow down to BMac or bow out.

2. Redemption for Kane Williamson

Saturday's closing moments against Australia weren't the first tense batting moments for Kane Williamson. A year ago at the World Twenty20 in Bangladesh, he was in the middle against Sri Lanka for a similar batting scare in another low-scoring thriller.

In what was effectively an elimination game in the last match of the group stage, New Zealand bowled out Sri Lanka for 119 and Williamson was the one New Zealand batsman who resisted an epic fight from Sri Lanka's bowling attack. Williamson was the only New Zealand player to reach double figures in a stunning collapse and his 42 accounted for 70 percent of New Zealand's runs. Despite all the carnage around him, New Zealand still held hope of a win until he was run out for the eighth wicket in a mix-up with Trent Boult.

On Saturday, Williamson was in the middle during a similarly chaotic collapse, but this time held his nerve long enough to lead New Zealand to victory. Just when it appeared that Australia might pull off a memorable comeback, Williamson snuffed out Australia's hopes with a six to seal the match and finish 45 not out.

3. New Zealand channeling Australia circa 2007

The Kiwis might have taken the adventurous route to victory Saturday, but they are still undefeated so far in group play (4-0-0). Although it is hard to match the number of legends Australia had on their undefeated squad at the 2007 Cricket World Cup, the 2015 version of New Zealand is doing its best to emulate them.

McCullum is as merciless as Adam Gilchrist at the top of the order. At No. 3 is New Zealand's most technically astute run machine in Williamson, a la Ricky Ponting for Australia. Corey Anderson is a hulking allrounder in the middle order who contributes as much with bat and ball as Andrew Symonds did. New Zealand's bowling unit of Daniel Vettori, Trent Boult, Adam Milne and Tim Southee is as varied and potent as Brad Hogg, Nathan Bracken, Shaun Tait and Glenn McGrath were for Australia.

New Zealand is full of charisma, shuts down the opposition in the field and has done just enough with the bat to win games. Most important, they have the inside track atop Pool A and, as a result, would host a home semifinal rematch at Eden Park should both teams progress to that stage. If New Zealand loses this tournament after the start they've had, it would be a tough pill to swallow.

4. India yet to be tested

Coming into this tournament, India's chances of repeating as World Cup champions looked very slim. They went through a nightmare pre-Cup tour of Australia, where they had not won a single match and pitch conditions were not going to change to make life any easier for them.

Somewhere in between the end of India's tri-series with England and Australia and the start of the World Cup, a switch flipped. After another win Saturday, this time versus UAE, India (3-0-0) now look like they'll cruise to the top of Pool B behind a resurgent batting lineup, confident bowling attack and energetic fielding unit. The only teams that look capable of stopping them are the two co-hosts.

5. Bowlers bringing back the balance

After Chris Gayle's double-century, AB de Villiers' 162 not out off 66 balls, and many other monstrous batting feats, it may give the impression that batsmen are dominating the tournament. However, bowlers have been just as prosperous in their own way.

There already have been seven hauls of five wickets or more, two short of the number through the entire 2011 Cricket World Cup and five short of the overall record (achieved in 2003). New Zealand's win against Australia became truly gripping to watch because it appeared that a wicket could fall at any moment. Sixes used to be rare, but their value has been cheapened with the advent of Twenty20 cricket. Not so for a bowler who turns in an extraordinary performance, such as those produced Saturday by Boult and Australia's Mitchell Starc at Eden Park.