Four years ago next week, Nathan Lyon was appointed to one of the most esteemed positions within Australia's team: leader of the victory song. It was an office held by the retiring Michael Hussey, and custom dictated that Hussey could choose his successor. Lyon, he believed, was a man of great character, who played the game for the right reasons. Even so, his decision surprised a few outsiders, for Lyon was yet to play 20 Tests, and hardly spoke a word in public.

But Hussey's judgement, as with his shot selection, was impeccable. Lyon went on to become Australia's most successful Test offspinner of all time, and is now the team's most experienced player. Since Hussey departed, Australia have won 22 Tests and Lyon has played in every one of them. And yet, on the fourth evening against Pakistan at the MCG, he found himself on the precipice, staring into an uncertain Test future.

"I'm not sure. That's up to the selectors," the captain Steven Smith said at stumps on day four, when asked if Lyon was a certain starter for next week's Sydney Test. His backing of Lyon seemed tepid at best. All summer Lyon has struggled to find vocal support from those in positions of power. Had Steve O'Keefe not been injured, he would likely have replaced Lyon for the final Test against South Africa in Adelaide.

And so Lyon arrived at the MCG on the fifth morning acutely aware of his perilous position. He had taken 1 for 115 from 23 overs in Pakistan's first innings, and nine wickets at 66.66 for the Test summer. When Smith threw him the ball in the 12th over of Pakistan's second innings, with the visitors wobbling at 2 for 25, Lyon needed to deliver. As it happened, Lyon's spell turned the match and made Australia's remarkable victory possible.

With the first ball of his fifth over, Lyon found some extra bounce and induced an error from Younis Khan, one of the world's finest players of spin. At short leg, Peter Handscomb snapped up a good catch low to the ground. Pakistan were 3 for 63.

Two balls later, Lyon's bounce once again brought a wicket. Pakistan's captain, Misbah-ul-Haq, could not control his sweep and top-edged a catch behind square on the leg side. Pakistan were 4 for 63.

And on the brink of tea, Lyon struck the blow that gained Australia access to Pakistan's lower order, when Asad Shafiq was caught by Handscomb at bat-pad. Pakistan were 5 for 89.

Smith later said the Shafiq wicket was the point at which he really started to believe Australia had a good chance of winning. And yet that was Lyon's last over for more than an hour. Tea came and went, and upon the resumption, Smith had Mitchell Starc and Josh Hazlewood, and then Jackson Bird in action before calling on Lyon for a second spell.

"He was bowling beautifully, there's no doubt about that," Smith said of Lyon. "But the ball was still hard and it had just started to reverse, so I thought it was a great opportunity to give Starcy three overs and have a crack with that. We know that when the ball is a bit harder and reversing it brings in both sides of the bat and I thought that was just an opportunity for that straight up. That was my plan."

Hazlewood did indeed make a breakthrough, and Lyon was not called on until 50 minutes after tea. He did not claim another wicket, but the fast men did the job, and Australia secured a win that seemed to come from nowhere. Lyon had turned the match for Australia, and had stepped back from the precipice.

"It doesn't matter who takes the wickets," Lyon said on Channel Nine after the win. "We're going out there to take 20 wickets and win games of cricket for Australia. If that means Josh takes all 20, or Birdy takes 19 and Mitchy takes 1, who cares? If we're winning games of cricket for Australia, I'm all for that."

Great character indeed. And so Lyon leads the team victory song once again. If he wasn't a certain starter for Sydney on the fourth evening, 24 hours later he most certainly was.

Brydon Coverdale is an assistant editor at ESPNcricinfo. @brydoncoverdale