India play Australia in five Tests starting Friday in Perth after their first red-ball series defeat at home in more than a decade exposed the visitors' growing vulnerabilities.

India won 2-1 against Australia on both of their last two Test tours, but suffered a 3-0 whitewash at home to New Zealand last month.

AFP Sport looks at five problems India face ahead of the series, which is crucial in deciding the finalists of the World Test Championship.

- Kohli and Rohit struggling -

Rohit Sharma and Virat Kohli were both poor with the bat against New Zealand.

Skipper and opening batsman Rohit managed just 91 runs in three matches and Kohli only 93, including four single-digit scores across six innings.

Coach Gautam Gambhir backed his premier batsmen as "incredibly tough men" ahead of the side's departure for Australia, and this will be the time to prove it.

Doubters say there are signs of a longer-term decline in the 36-year-old Kohli.

For years one of the world's most feared batsmen, he has managed only two Test centuries in the last five years.

As for Rohit, batting great Sunil Gavaskar warned he could struggle in particular against Australian quick Mitchell Starc's "lengths and lines".

The 37-year-old Rohit appears set to miss the first Test following the birth of his second child.

- Opening woes -

Rohit's form has damaged India's ability to start well in recent times and placed the onus on young opening partner Yashasvi Jaiswal to set the tone.

Despite his recent struggles Rohit would have opened in Perth so now Indian selectors are pondering their replacement options.

KL Rahul looks most likely to open with Jaiswal, but he has also not been in great touch and was dropped from the final two Tests against New Zealand.

Former coach Ravi Shastri had suggested Shubman Gill could be an option to start the innings, but he also looks set to miss the opening match after reportedly fracturing a thumb.

The uncapped 29-year-old Abhimanyu Easwaran has emerged as a contender.

- Too much on Bumrah? -

Pace spearhead Jasprit Bumrah has lacked support at the other end with senior pacer Mohammed Shami injured and fellow quick Mohammed Siraj struggling to take wickets.

Siraj claimed two wickets from three innings in the New Zealand series and lost his place to Akash Deep.

According to media reports, Shami could make a late entry into the Test squad after an impressive comeback from injury in a domestic match and form a new-ball combination with Bumrah.

As vice-captain, Bumrah will find himself stepping up to lead the side if, as expected, Rohit misses the Perth Test.

Former Australia all-rounder Brendon Julian has said, taking all that into account, it "could be a lot of pressure on your opening bowler".

- Gambhir under the cosh -

Gambhir, a former opening batsman and successful Indian Premier League coach, took over a triumphant national side which won the T20 World Cup in June.

The honeymoon did not last long, with pundits in India questioning Gambhir's tactics in the series whitewash to New Zealand.

"I don't think as if I am feeling the heat," the 43-year-old fired back.

Former batsman Sanjay Manjrekar lambasted Gambhir's public defence of his side after the loss, suggesting that Rohit and chief selector Ajit Agarkar were "much better guys to front up for the media".

Former Australia captain Tim Paine was also scathing of Gambhir, saying that "the concern for India right now isn't Rohit Sharma's batting, isn't Virat Kohli's batting -- it's their coach and his ability to stay calm under pressure".

- In a spin -

Veteran spinners Ravichandran Ashwin, 38, and 35-year-old Ravindra Jadeja were outshone by their New Zealand counterparts on home soil.

Spin duo Mitchell Santner and Ajaz Patel bamboozled India's batting lineup whereas Ashwin and Jadeja struggled by comparison on what should have been favourable home conditions.

Only one of the Indian slow bowlers is expected to make the XI on bouncy Australian pitches where quicks will likely play a larger role.

Off-spinner Washington Sundar, 25, is in the mix after taking 16 wickets in two matches against New Zealand.