Paceman Pat Cummins took both the wickets for the hosts. Kohli chases second ball which is full and wide outside off and Tim Paine drops a tricky catch.
"It's a massive morning".
"Things can change, momentum can change and I don't think we're far away", he added. India chose to bat first on a greenish pitch and from the outset, that decision appeared the correct one as a slow wicket offered little for the bowlers.
It is perhaps the most important day in the life Vihari, who is just two Test matches old but has showed great determination and focus whenever he has come out to bat in whites.
The four-test series is level at one-all.
The four-test series is evenly poised at 1-1 after Australia's victory in the second contest in Perth, with the MCG's drop-in wicket under scrutiny after producing a lifeless draw in the Ashes series against England previous year.
Agarwal, who has been in fine form in domestic Indian cricket, scored his first Test runs with a three through the covers off Josh Hazlewood and he had plundered 17 before the more cagey Hanuma Vihari, promoted to open from number six in Perth, troubled the scorers.
Pujara will resume on 68, eyeing his second ton of the series.
It was a remarkable effort from Cummins, who claimed 2-40 from 19 overs after forcing both openers into false shots on a lifeless pitch. "Saying that, I would have liked to have gone on and be there at the end of the day", said Agarwal. "We want to lead our team well and play good cricket which the public want to see". "The majority of this decision has been based around it's a long series, we've played on a lot of hot days and our bowlers have had a big workload", he said.
Cummins was the pick of Australia's bowlers. "They kept it tight and they were attacking".
India ground their way to 123 for two at tea with the patient Cheteshwar Pujara unbeaten on 33.
Kohli and Paine clashed a few times in the tension-filled Perth test but the Indian captain played down the altercations, saying sparks are bound to fly when two competitive teams meet.