The heat will be on both Smith and Labuschagne when Australia get to bat again in the first Test against India at Optus Stadium.
Smith was out for a first-ball duck on Friday when he was trapped lbw by an inspired Jasprit Bumrah.
Australia were bowled out for 104 in reply to India's 150, with the visitors in the box seat to win the first Test.
Smith has now been dismissed lbw four times from his past five first-class innings.
Jasprit Bumrah celebrates dismissing Steve Smith first ball. (Dean Lewins/AAP PHOTOS)
Labuschagne's dig was painful to watch on Friday, the 30-year-old copping a series of body blows on the way to making just two off 52 balls.
He was eventually put out of his misery when Mohammed Siraj trapped him in front.
It continued a worrying trend from Labuschagne, who has posted just one half-century from his past nine Test innings.
He has now gone 17 Test digs without a century, and he looked all at sea against India's star pace attack on day one.
Smith has gone 22 Test innings without a ton, with his closest effort being an unbeaten 91 while opening against West Indies in January.
Leading into the Border-Gavaskar series, Cummins was confident of a turnaround from Smith, who is a notorious fidgeter and constantly tries to master the best bat grip.
"I know every summer the conversation's around his hands and whether he's found them or not. I can report they've made their way to Perth, his hands, which is always good," Cummins said.
Former Test opener Simon Katich believes Labuschagne was far too defensive.
Marnus Labuschagne is struck on the body during his first innings. (Dean Lewins/AAP PHOTOS)
"Labuschagne ... in the last couple of seasons hasn't been anywhere near his best and I think mindset in particular (has played a part)," Katich told the Seven Network.
"In what I saw of him yesterday ... 92 per cent of the balls he faced he either defended or left. That's not how you survive on this wicket.
"I saw he entered the series saying he wanted to bat like (Cheteshwar) Pujara, (bat) for long periods of time.
"The problem is, if you're having to absorb six balls an over and you're not looking to use your bat, you can't get off strike.
"The pressure built. In the end, the damn wall broke and he got lbw and he's a better player than that. That to me was about his mindset."
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