Steve Smith 'weakness' exposed during 'incredible' moment

New Zealand may well have solved one of cricket’s toughest mysteries - how to get Steve Smith out.

It took a piece of brilliance in the field but once again, Kiwi quick Neil Wagner had Smith’s measure.

The former Aussie skipper made patience his priority on an opening day that saw him unbeaten on 77.

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However, that patience appeared to crack after the drinks break during the opening session on day two when he was again undone by the short ball.

The Kiwis used the short-pitched tactic superbly in the opening Test and vowed to continue the approach at the MCG.

On day one, Smith was able to withstand the barrage and looked destined to notch up his 27th Test century on Friday when he moved into the 80s.

However, Wagner had other ideas - banging in a wicked bouncer that leapt off the MCG pitch and caught Smith off guard.

The ball looped up off Smith's gloves and into the gully where Henry Nicholls took a superb one-handed catch to send the 30-year-old packing.

Nicholls appeared to have misjudged the flight of the ball but managed to snaffle the catch by his fingertips as Smith fell to Wagner for the third time this series.

The incredible moment left viewers in awe on social media.

Smith spent the previous week perfecting his answer to short-pitched bowling after being caught out by New Zealand on the pull shot in his last three innings against them.

Short ball continues to trouble Smith

The former Aussie captain was clearly unhappy with himself as the short ball again proved his undoing in Melbourne.

New Zealand are among the best planners in the world and no doubt believe they have found a weakness in Smith.

They had him out twice off bouncers with dominant legside fields at Optus Stadium, where Smith scored just 43 and 16 in his two innings.

It's no coincidence Smith's strike-rate of 35.41 this series is by far and away the slowest scoring rate of his career.

Smith's wicket had the potential to be a crucial strike for the Black Caps in Melbourne, who are staring down the barrel of a big first-innings score.

But Travis Head (57no) and Tim Paine (33no) ensured he would be the only dismissal of the first session, with both desperate to post their first big scores of the summer.

By lunch, the Aussies were looking solid at 5/336.

Paine in particular has scored at a brisk rate, upping the ante on his arrival with four boundaries from his 45 balls faced.

Smith had looked set for his first century of the summer, before he became Wagner's second scalp of the innings after opener David Warner on day one.

The Australian star got one that rose steeply at him from the left-armer, before it collected his handle as he jumped to combat it and the ball lobbed to gully.

Nicholls had to leap high to take the catch, ending Smith's shot at becoming the first to hit centuries in five straight MCG Test appearances.

Australia's former captain had previously played the short ball well, limiting and controlling his pull shots and getting out of the way of most bouncers.

But Wagner's delivery showed real life in an MCG pitch that has been accused of being too dead in recent years.

Smith's dismissal left him with an average of 128.71 at the ground, just above Don Bradman's previous record mark of 128.52.

With AAP