India skipper Virat Kohli will return home on paternity leave after the first Test against Australia.
Cullinan believes the visitors will definitely miss the competitive edge Kohli brings to the table as a leader but they also have capable replacements available to be able to still hold their own against the Aussies.
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Kohli will return home after the D/N Test in Adelaide to attend the birth of his first child in early January, which will leave the likes of Ajinkya Rahane and Cheteshwar Pujara with bigger responsibility in Melbourne, Sydney and Brisbane.
In Rahane's case, he'll also have to step-up as skipper being a vice-captain. The right-hand batsman, who has started off his tour with a superlative hundred in the first warm-up game, has not yet had the experience of leading the senior national team abroad.
"Both are quality teams and will come hard at each other. Australia, in their own backyard, will always start as favourites but India are a tough side and it should be a keenly-fought series," Cullinan told the Times of India.
"India will miss the attitude and competitiveness that Virat brings to the team. His sheer presence gives a boost to the Indian dressing room."
"However, with Virat not in the side, it's an opportunity for others to step up. India have the likes of Cheteshwar Pujara, Ajinkya Rahane and others to shoulder the responsibility of scoring those crucial runs against a quality Australian bowling line-up," he added.
Cullinan also thinks the visiting side will be properly accustomed to those conditions by the time the Test series begins on December 17.
The Indians arrived down under early November to adhere to the necessary quarantine regulations amid COVID-19 pandemic and are currently busy with the white-ball leg of the Australian summer.
They also have two pre-series warm-up fixtures lined-up before taking the field at the Adelaide Oval.
"When you come to a new country, adjusting takes time. A few of the players in the Test series are featuring in the limited-overs leg of the tour," stressed Cullinan. "The rest of the Test specialists have been training in these conditions and that should work in India's favour ahead of the Adelaide Test."
Cullinan, meanwhile, also gave his views in the debate around India's T20I captaincy. Ever since Rohit Sharma led Mumbai Indians (MI) to their fifth IPL title in UAE on November 10, prominent voices have suggested a takeover from Kohli, whose Royal Challengers Bangalore (RCB) couldn't once again reach the coveted crown.
"Has Virat done badly in T20s? No, he hasn't. Then why change the captain. That's my view," he said.