Spin Australia's best weapon to win in India?

Left-arm spinner Ashton Agar could turn out to be Australia's X-factor and should be considered as their 'second spinner' in pursuit of the visitors' first Test win in India since 2017, said former coach Darren Lehmann.

Agar, who has only five Tests under his belt, returned wicketless during Australia's last Test against South Africa in Sydney but, on Indian conditions, the finger spinner could be successful, the former coach said.

"Having been there, I'm probably more inclined to play finger spinners," Lehmann, who was the coach of their 2017 victory in Pune, said on Australian radio station SENQ.

At that time, left-arm spinner Stephen O'Keefe played the match-winning role by bagging 12 wickets.

Australia begin the marquee four-Test series against India at Nagpur from February 9.

It was at the same venue last week the left-arm spinners from both sides wreaked havoc, bagging a total of 23 wickets in a Ranji Trophy match.

Vidarbha's Aditya Sarwate led the show with a match haul of 11/81 as they defended the lowest Ranji Trophy total of 71 in an 18-run win over Gujarat.

"It just gets through the air quicker and some spin and some don't. The leg-spinners sometimes spin it too much, if that makes sense... (for finger spinners) some skid on and you get beaten on the inside and you get an LBW.

"That's probably why they're looking at a finger spinner. We certainly did that four years ago (2017) and Steve O'Keefe bowled India out basically on his own in one of the last Test matches to win there.

"That's why I'd be looking at someone like an Agar, bat a little bit, bowl as that second spinner," the 52-year-old added.

Agar is the only left-arm spin option in Australia's touring squad which have leg-spinner Mitchell Swepson and uncapped off-spinner Todd Murphy in its ranks.

He also thinks having the luxury of Swepson in the touring party will be important should conditions favour a leg-spinner being included at any stage.

"I can't believe there was talk of him (Swepson) not going, talk about balance of the side, if you get to pick 18 players, you want a pretty balanced squad," Lehmann added.

"Most of the time we only take 15 (players) over there. They've got the extra spinners, there's plenty of options, there's no tour game, so they'll work out the best option to win over there I'm sure.

"It does look like a pretty good squad. If it suits to play the leg-spinner as the second spinner, then good on him."

Lehman's former side need a 4-0 whitewash in India to book a place in the World Test Championships final.