The 23-year-old left-arm finger spinner made his test debut as a teenager in the 2013 Ashes series, starring more with bat than ball in two matches against England that remain his only experience of the longest form of the game.
With Steven O'Keefe having been dropped despite a brilliant tour of India earlier this year, however, Agar is in the driving seat to get the nod ahead of uncapped leg-spinner Mitchell Swepson in a twin spin attack with Nathan Lyon.
The tourists were robbed of their only practice match by the Dhaka rain on Monday, which Lehmann said made it even less likely he would radically overhaul his team from that which finished the tour of India in March.
"We obviously haven't played too much, so we're fairly settled in where we want to go," he told reporters in the Bangladesh capital.
"That decision will be made later, once we start to have a look at the test wicket and the conditions. Most likely, I think we'll play two spinners."
Agar toured India with Australia earlier this year but never got a chance to play as his fellow left-armer O'Keefe took 19 wickets at an average of 23.26, including 12 in the first test at Pune.
O'Keefe, 32, was fined A$20,000 ($15,838) for "highly inappropriate behaviour" towards a female cricketer while drunk at an award ceremony in April, however, and was dumped for the Bangladesh tour in favour of the younger man.
"Steven was excellent over there but we've decided to go with Ashton," Lehmann said.
"He's got the all-round game and hopefully he'll take it to the next level so if we wanted to play three quicks he could bat up the order, for example. He gives us a lot of flexibility in that way.
"Young Swepson is a good prospect as a leg-spinner ... it's really tight between all the spinners but Ashton himself has batted really well, he's a gun fielder and he's got his length right with the ball..."
The first test starts on Sunday with the second in Chittagong scheduled from Sept. 4-8.
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First Published: August 22, 2017, 2:05 PM IST