Smith (119) and Shaun Marsh (130) combined for a record Australian second-wicket stand against Sri Lanka of 246 but their dismissals within eight runs of each other in the afternoon were as concerning as the exposed raw fish for sale in the local markets.

The tourists' troubles against spin then returned, for they would lose 7-96 to be dismissed for 379 — a lead of 24. Veteran left-arm finger spinner Rangana Herath, still feeling the pain of a nasty hit to the groin when batting on Sunday, again tormented the tourists, claiming 6-81, leaving him with 20 scalps in the series and the 25th five-wicket haul of his career.

The loss of Smith and Marsh had turned the focus onto all-rounder Moises Henriques, who has had little cricket on tour but was suddenly thrust into the No.5 spot, presumably as a specialist batsman, in his first Test since 2013.

When he lunged early at a delivery from Herath which spun late and was stumped, his selection remained questionable. He has averaged a modest 31.91 in first-class cricket and almost certainly won't feature in the home Test series opener against South Africa in November. Oddly, he had not been given a bowl in the 141.1 overs Sri Lanka had in their first innings.

The form of wicketkeeper Peter Nevill (14) has emerged as an issue, for he has only 49 runs at 9.8 in five innings. The tourists, with a fragile top-order, need more from a No.7 batsman, particularly when they return to the sub-continent in February. In 15 Tests, he has a top score of 66, averaging 22, and has yet to rubber-stamp his position.

Mitch Marsh conjured a timely half-century, the second of his 18-Test career, and the first since his second match, to help ensure a lead on a wearing Sinhalese Sports Club ground wicket which could be treacherous come a fourth innings.

At stumps, Sri Lanka, having negotiated the five overs on offer, were 1-22. Spearhead Mitchell Starc had added his 23rd wicket of the series, leaving him needing three more to equal the record for the most wickets by a fast bowler in a campaign in Sri Lanka.

Sri Lanka coach Graham Ford said the contest was evenly poised after a "roller-coaster" day where his side had shown great "maturity".

"It's been a heck of a Test match - Test match cricket probably at its toughest," he said.

"Both sides have outstanding players capable of changing the flow of the match."

In a lighter moment, Ford joked that Herath was his new sporting hero, ahead of Roger Federer, after his efforts with the ball and bat. But, in the same breath, he underscored the importance of the wily spinner.

"He showed so much fight. He is basically bowling on one leg, also taking on the quicks when he was batting," Ford said.

Smith, in posting his 15th Test ton, and Marsh had carried their side to safer shores by handling the spinners, largely with aplomb, in a robust 433-ball partnership, besting the 170-run stand by Kepler Wessels and Graham Yallop in Kandy in 1983. It was also Australia's fourth-highest stand of any kind against Sri Lanka.

Former Australian captain Michael Clarke took to Twitter to congratulate the pair. "Good on you Sos. Great team man," he said once Marsh had swept Dilruwan Perera for four to confirm his fourth Test ton. Marsh's nickname is derived from Son of Swampy, the nickname for his father, Geoff, the former Australian batsman.

Marsh, no doubt, was delighted to have his wife Rebecca and two-month-old son Austin in the crowd. They had arrived on Sunday night.

Clarke added about Smith: "Brilliant. Leading from the front."

That Smith had done, having promoted himself to No.3 after Usman Khawaja was axed. Through this knock, he became the youngest Australian to 4000 Test runs, beating Ricky Ponting by 265 days, and the third-fastest Australian in terms of innings.

Marsh's fourth Test century has put the national selectors in a tough spot. They have indicated dumped opener Joe Burns will be firmly in the hunt for a recall come the South African visit but Marsh now has centuries in his past two Test innings.

In his seventh incarnation as a Test cricketer, he had to make way after his ton against the West Indies in Hobart last summer for a returning Khawaja, who had recovered from a hamstring strain.

The selectors will also need to decide if Khawaja, also dropped for this dead rubber but having enjoyed a strong home campaign last year, immediately returns despite his troubles with spin here.

Marsh's problems have been against quick bowling early in his innings, with a propensity to "nick off". If he struggles to retain his spot at home, he almost certainly will be in the squad heading to India for four Tests from February.