A third-umpire decision has created a huge talking point early in the fifth Border-Gavaskar Test, with Virat Kohli surviving a contentious catch call on the first ball he faced at the SCG.

Walking out at 17/2, Kohli edged a delivery from Scott Boland towards Steve Smith at second slip, with Smith reaching low to his right.

With the red Kookaburra wedged between his thumb and index finger, Smith went on to scoop the ball in the direction of Marnus Labuschagne - who caught the ball - before Kohli stood his ground.

Reviewing the replays, third umpire Joel Wilson deemed the ball touched the ground in the process of Smith trying to take the catch and thus not satisfying the conditions of a fair catch per MCC Law 33.

Through the limitations of various replay angles, the decision was not one agreed upon unanimously in the cricket community.

Former Test umpire Simon Taufel explained why the review was hard to judge on Channel 7's coverage of the match.

"Depending upon which side of the fence you sit on you could probably build a case for either decision to be given," he explained.

"Listening to Joel Wilson's language there (making the decision), where he said the fingers were underneath the ball and then he's seen it roll on to the ground, by his own language he is telling us that he believes he's seeing that ball on the ground.

"So, there are two things that the TV umpire here is looking for. One is fingers underneath the ball. He was satisfied there. But then he believes through those pictures that he's clearly seen the ball on the ground.

"I can certainly understand what the third umpire's done there. He believes he's seen the ball on the ground and called it way he's seen it. Normally the ICC protocol on fair catches is if you see the fingers underneath the ball, that's good to maintain a fair catch.

"But here's the problem: the on-field umpire's no longer have the soft signal and make the decision, it's purely in the hands of the television umpire now."

Elsewhere though, former players, broadcasters and Smith himself weren't of the same view.

When asked if he had kept the ball alive in the process of taking a catch, Smith was certain when speaking to Fox Cricket at the lunch break: "100% (the catch was fair). No denying it whatsoever. But the umpire's made the decision and we will move on."

In the Fox Cricket commentary box, Mark Waugh felt the catch was completed successfully.

"It would've been a great catch…I think it was (fair)…he (Smith) is not happy," he said.

"You see his right finger just underneath it…I think he's got away with one there, (Virat) Kohli."

During a drinks break in the first session, former England captain Michael Vaughan and Australian skipper Alyssa Healy gave their verdicts on Fox Cricket.

"You need a little bit of fortune as a batter, and I think Virat Kohli has had that fortune on (his first ball). I think that's out. Australia should have had their third wicket," Vaughan stated.

"It's a tricky one, because if you watch that in live motion, it looks out – and Steve Smith obviously felt like he got a hand underneath it as well," Healy added.

"But in the modern day with the rulings that they've got, if (it looks like) any little piece of ball on the ground, the umpire's more likely to say it's not out."

However, the likes of former India player and now commentator Irfan Pathan said the umpire got the decision right while Mark Nicholas also suggested the decision was likely correct.

Kohli remained not out at the lunch break, though was eventually dismissed early in the second session of day one, edging another Scott Boland delivery, this time to Beau Webster at third slip.