Australia are a tale of two openers.
Both products of Sydney's eastern suburbs - though Ed Cowan has a bookish Rose Bay air about him compared to David Warner's muscular and frenetic King's Cross wide boy - their disparate approaches are the strength of their partnership.
Warner is exhilarating, Cowan measured. Where the former likes to take the attack to the bowlers, the latter lets them come to him.
But the marriage of the two left-handers is starting to fray at the edges.
Their ardour may not be cooling on the path to irreconcilable differences that leads to inevitable divorce, but a tension or two has crept into the relationship.
And it was clearly evident at the SCG when Cowan was run-out after his tardy response to his partner's call for two early in Australia's first innings.
As sluggish in his running as Warner was crisp in his stroke play, Cowan paid the price for dawdling the first run and then hesitating for the second.
Nuwan Pradeep's rapid response and throw from mid-wicket set the standard for Sri Lanka, whose sharp fielding would extend to two excellent run-outs and three splendid catches.
It was the second time Cowan had been run-out this summer and the third time this series that he, Warner or No.3 Phil Hughes was run-out in a mix-up with one of the others.
Cowan has now played 13 consecutive Tests, but his place in the team is more tenuous than it was at the start of the summer. His 686 runs have come at the useful, but not convincing, return of 32.66.
Shane Watson is in the wings and contemplating another career change, with consequent nervous moments for those players seemingly not gifted with his right to choose his role.
Cowan has much in common with 1970s openers Alan Turner and Ian Davis.
All three played a dozen or so Tests, each averaged around 30 and had the glory of a sole century.
Those attributes confirmed their capacity to perform at Test level, but also illustrated their inability to nail a permanent place in the team.
Where Cowan was disappointed early, Warner's heartache came late in the piece.
He rocketed out of the blocks and had 29 of the first 30 runs by the time the fifth over started.
Yet his onslaught was controlled, even clinical, with his watchwords authority and timing and his focus on punching the ball with a short backlift and abbreviated follow-through against an undermanned attack.
A century in the session app- eared likely, rather than possible, when he brought up his 50 from 37 deliveries, but he was denied the strike for large portions of the next hour or two as Hughes made merry.
"I had the best seat in the house when Davy was going," Hughes said.
"But I never felt in. You had to play the ball as late as possible on that wicket.
"I batted with Davy a fair bit at NSW and he is great to bat with because he takes the pressure off by getting off strike a lot and he scores at a very good rate."
Gliding the quicks in his favourite area through point, although his more rounded game was on show with a series of front and back-foot shots through the leg side, Hughes appeared even more effortless than his flamboyant off-sider.
But as Hughes' impact increased, Warner lost his momentum until, inevitably, he produced a false stroke.
Warner had previous scores of 57, 68 and 62 in the series but was again denied the conversion to three figures.