There was really only one way the equation was supposed to play out.

David Warner resuming on 60 not out, Cameron Bancroft on 51. The fifth day, with 56 runs needed for a foregone win.

In any familiar world, the aggressive Warner would monopolise scoring and smash a hundred, while the patient, quiet, junior partner blocked the odd ball at the other end.

Except that isn't what happened at all.

Warner deliberately avoided it. Instead of gobbling the available runs, he put himself on rations, then fed his nest-mate bit by bit so the youngster would grow up big and strong.

Warner is a fine exponent of the junk-time hundred. Two Januaries ago in Sydney, emerging from three full days of rain to smash a West Indies attack so thin the bowlers didn't cast shadows.

The same ground a year later, battering a broken Pakistan before the game's first lunch break.

In the 2013-14 whitewash, England twice copped second-innings batterings in games already lost, once in Brisbane and at Perth. The Gabba was home to another declaration smash against New Zealand in 2015.

This isn't to disparage Warner — when you have 20 Test centuries in as short a time as him, some will be more important than others.

He has made his share with the pressure on, starting with his first when he carried his bat against New Zealand on a green seamer in a buttock-clenchingly narrow loss.

Cashing in when the easier chances appear is what a good player must do. It gives your team momentum, it keeps opponents at a disadvantage, it pads your record against the runs of bad luck that counterweigh the good.

It also takes skill to ram home the advantage. When Warner lays into a set of bowlers, he shows he still has the attacking intensity and skill that got him into the Australian team.

The ability to switch modes is one of cricket's more impressive talents.

David Warner in action of Day 4 of the First Ashes Test match. ( AAP: Darren England )

It intimidates future opponents, and shows how he has added layers to his game.

Fundamentally, you can't afford to be wasteful. Cricket is a tough sport, and its easier opportunities come rarely.

In terms of off-field factors, this kind of Warner carnival action entertains crowds, pleases viewers, and adds spice to straightforward proceedings.

So that was exactly what you would have expected in this first Ashes Test of 2017. Warner had perfect licence to entertain an excellent last-rites crowd of 6,154.

He could have pogoed the ball to all parts, sent a few into the multi-coloured seats, and crushed the win in half an hour.

Or he could have perished trying, and given the Barmy Army something to cheer.

But here, something very different played out instead.

Warner's first order of business was a back-foot punch for three.

On the third anniversary of Phillip Hughes' death, that took Warner to 63 not out, the score still symbolically associated with his friend and teammate.

Warner looked to the heavens in a quiet moment of acknowledgement.

From there, Warner never launched. He stayed with the ground crew. Taking a single, then letting Bancroft soak up an over. Taking a single again. There were no big shots. The score meandered. What was going on?

Debutant Cameron Bancroft was not nervous to go after the bowling as Australia closed in on victory. ( AAP: Darren England )

Five times, Warner knocked a single run from the first ball of the over. Four times from the second ball, and three times from the third. It became clear. Warner was turning over the strike to give his young partner as much as possible.

There is a long series ahead. The opening pair is vitally important. Bancroft faced 19 balls in the first innings.

Going into the Adelaide Test half-baked could have had knock-on effects for him and the team.

By the time this second innings was done, Bancroft had absorbed 182 deliveries, at a strike rate less than half his partner's.

He'd had the chance to bat from both ends, facing all the bowlers, having to move and re-mark his guard and recount the field.

This tallied with the previous evening's approach. Had Warner gone harder earlier, Australia could have claimed the extra half hour and finished the game in four days.

Perhaps there was a broader tactical aspect, in that England would have had more to gain from an early finish.

Australia's bowlers were already resting up, while with four days until the Adelaide Test, each extra over in English legs increased their disadvantage.

But Australia had the bonus of having their debut opener come back the next morning, for the experience of starting an innings again.

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To rebuild into the next day, to face world-class practitioners in Stuart Broad and Jimmy Anderson, and to do so without any personal pressure, having already made a fifty, nor any team pressure, with the result in the bag.

In short, it was the highest-quality net session a batsman could ever have.

While it meandered on with occasional singles, the Warner century remained possible.

On 79, he whacked a four and a two, and the late charge could have been on. But immediately he changed tack, changed strike, and let his partner continue.

In the end Bancroft had the blessing to go, taking three boundaries from a Chris Woakes over.

After a day of solid apprenticeship, hitting the winning runs in an Ashes Test would give the kind of feelgood factor that could carry him through the series.

He was certainly in high spirits during his media conference, relating his peculiar introduction to Jonny Bairstow with a comedic turn of phrase and a highly confident delivery.

Warner remained 87 not out, a milestone so close yet unpursued.

When you already have 20 centuries, it must be easier to decide that some don't matter.

More important was an Ashes series, and taking care of every detail to give the best chance of a win.