Pakistan makes a tremendous fist of a tough run chase thanks to a couple of costly drops, but a debatable dismissal helped hand the Aussies a hard-fought victory on day four of the Boxing Day Test.

Here are five quick hits from day four at the MCG.

1. Pat Cummins's mystery edge

Aamir Jamal has bowled some terrific deliveries in this Test without much luck — but perhaps he got some with his first wicket in the second innings.

Cummins drove at a ball that nipped back into him and passed by the inside edge.

Muhammad Rizwan was convinced, as were the slip cordon and, crucially, umpire Michael Gough, who raised the finger.

However Jamal didn't seem overly confident and Pat Cummins was certain he hadn't touched it, so upstairs we went for a review.

Nothing on hot spot.

A possible hint of daylight between bat and ball?

The faintest of murmurs on snicko though as the ball passed the bat.

Not enough evidence to overturn the on field decision and Cummins had to go.

2. Alex Carey's valuable runs

One of the nice guys of Australian cricket, although there are more of them these days than there used to be, Alex Carey became public enemy number one for the English during the Ashes for … reasons.

It did seem to have an impact on his game as his body language and results would suggest and, while his glovework remained sound, the runs stopped flowing after a 66 in the first innings of the series in England, with a top score of 28 after that.

In this Test, he was given a good job for a number seven, coming out after the hardest work had been done by Mitch Marsh and Steve Smith, but with runs of substance still up for grabs.

The tidy left-hander made it through a tricky period to stumps on day three, watching Smith fall in the evening, leaving Carey to bat with the tail on Friday.

As good keeper/batters do, he chose when to attack and defend, opted against protecting competent batters like Mitchell Starc, Pat Cummins and Nathan Lyon, but farmed the strike more alongside number 11 Josh Hazlewood.

All the while he carted eight boundaries as he reached his first half-century from the past six Tests and took Australia's lead beyond 300 for a psychological and numerical edge over its opponents.

3. Missing out on Masood

After Mitchell Starc got Abdullah Shafique to put the brakes on the start of Pakistan's chase, Nathan Lyon thought he'd ripped out the accelerator when he hit Shan Masood in front and Michael Gough raised the finger.

That would have left Pakistan 2-21 in the eighth over of a 317-run chase, but technology intervened.

Pakistan's captain quickly reviewed and the rock-hard new ball on a lively pitch with Lyon's trademark loop and bounce was Australia's undoing.

The ball tracking showed the ball bouncing well over the stumps and, although the Australian players could scarcely believe it, the right decision was reached and Shan made it to lunch alongside Imam-ul-Haq.

He carried on to a well made 60 and featured in a dangerous 61-run partnership with Babar Azam that gave Pakistan its first real signs of hope.

4. Attacking Rizwan dropped, Salman too

With Pakistan reduced to 4-146, still 169 runs behind, you might have thought the tourists would want to be careful, more circumspect for a while as they tried to re-boot their chase.

That's not how Muhammad Rizwan works.

Having faced five dot balls from Josh Hazlewood, Rizan's thought he should take advantage of some slower bowling when he could.

Nathan Lyon came in and Rizwan launched him for a massive six with a slog sweep over square leg — the longest part of the ground.

It was an astonishing shot to get off the mark and signalled the intent that Rizwan could continue to show.

Nathan Lyon should probably have got his revenge later on in the 56th over though.

First, Carey dropped a tough outside edge chance that skidded through and whacked the outside of Carey's glove. He was on 26.

The next chance came off his batting partner Agha Salman, a reverse sweep that popped up to a diving Steve Smith, just failed to hang on.

Two costly chances in the same over gave the impression things were slightly slipping away from Australia as they chased victory.

5. Rizwan's controversial wristband

Cometh the hour cometh the man — which always means Pat Cummins when Australia needs him most.

Muhammad Rizwan was starting to really find his straps, reaching 35 when he ducked and was hit by a bouncer that flew through to Carey behind the stumps.

But what did it hit?

Cummins thought and thought but decided to review caught behind at the last moment. It proved a good decision.

The replay appeared to show the ball brush the wristband of the glove before it hit the forearm.

Rizwan was adamant that the ball did not hit any part of the glove and hit him on the arm, showing umpire Wilson a huge mark.

"Straight off the glove champ," said one Australian fielder in the huddle.

Given the decision was not out in the middle, third umpire Richard Illingworth needed to be certain that the ball hit the part of the glove, and he was, to the fury of Rizwan.