Steven Smith is a machine. How else to explain the amount of moving parts, which to the human eye appear completely disjointed, yet produce such efficient, consistent results? How else to explain his record as second only to cricket's ultimate machine, Don Bradman, on the list of batting averages as Test captain (with a five-Test minimum)? How else to explain his monastic patience against Joe Root's ever-changing fields at the Gabba?

Yet Smith's celebration upon reaching his century was undeniably human - and not in the usual, cliched way (though he did kiss the badge of his helmet). To see Smith's determined stare in the direction of the change-room, and the double-punch to the national crest on his shirt, was to understand that this hundred was unusually special, coming as it did in his first Ashes innings as captain, and with his side in trouble.

Smith had walked to the crease on the second day with Australia at 2 for 30. Soon, they were 3 for 59. Then 4 for 76, in reply to 302. This was not how it was supposed to be. This was the Gabbatoir, the Australian cricket slaughterhouse at which no visiting team has won a Test since a 1988 West Indies side boasting Viv Richards, Desmond Haynes, Gordon Greenidge, Richie Richardson, Malcolm Marshall, Curtly Ambrose and Courtney Walsh.

And yet Smith did not panic. At times, Root pushed four men back to the boundary, testing Smith's patience. It took Smith until his 90th ball before he scored even a single run through the off side. Earlier, David Warner had run out of patience against a similarly defensive-looking field, trying to force the runs and instead sending a catch to short midwicket. But Smith was happy to wait. And wait.

Little changed in regard to his patience on the third day, even after Smith lost Shaun Marsh following a 99-run stand, and then the wicketkeeper Tim Paine. England attacked him with short stuff, set traps in the deep, and Smith would not be budged. At one stage, he faced Jake Ball with a deep square leg, deep midwicket, backward square leg, leg slip, mid-on, and no slips. Leg slip moved to silly point, and next ball Smith duly glanced a boundary where leg slip had just been.

There was nothing Root could do but take wickets at the other end. Even that goal ran aground when Pat Cummins settled in for an eighth-wicket stand that lasted 32 overs. By the time Smith finally lost the last of his partners, he had 141 from 326 balls, had batted for eight and a half hours, and had - most remarkably - given Australia a first-innings lead.

His 261-ball hundred was comfortably his slowest in Tests, beating the 227-ball century he made against India in Ranchi earlier this year. No Australian since Simon Katich in Hamilton in 2010 had compiled a slower Test hundred than Smith's Gabba effort, though he was a considerable distance behind the Australian record of 318 balls set by Bill Brown in an Ashes Test at Trent Bridge in 1938.

It is easy to become indifferent to Smith's achievements, so accustomed have observers become to his consistent high-scoring. So consider some figures for context:

No player in Test history has scored more runs or averaged more than Smith at the same stage of his career - that is, after 57 Tests. Smith has 5511 runs; next on the list is Sunil Gavaskar with 5460. Smith's average is 61.23; next on the list is Garry Sobers, who averaged 60.14 at the same stage. Even if Smith makes a duck in the second innings, he will remain ahead of Sobers.

It must be noted that Bradman played only 52 Tests, and scored 6996 at 99.94. But he is the only player with fewer than 57 Tests who sits above Smith for runs scored. And he is the only player who averages more - 101.51 - as Test captain than Smith's 72.46 (with a five-Test minimum).

What makes this all the more astonishing is that Smith started his Test career batting at No.8 and bowling legspin. He did not regularly bat at No.4 or higher until nearly halfway through his career.

At the same stage of his career Sachin Tendulkar had 13 Test hundreds, Ricky Ponting had 11, Brian Lara had 10, Rahul Dravid had 10, Mahela Jayawardene had 10, Jacques Kallis had nine, AB de Villiers had nine, Kumar Sangakkara had nine.

Smith has 21.

And it's hard to recall a more important one than this.

Brydon Coverdale is an assistant editor at ESPNcricinfo @brydoncoverdale