Warner’s demotion down the batting order was a great success in the recent three-match T20 series in South Africa.
The vice-captain was named man of the series, having totalled 130 runs in his new middle-order role.
Lehmann was suitably impressed with Warner’s form at No.4 in the 2-1 series win.
“But he could open in the first game. You don’t know, it just depends on the match-ups and what we like at the time,” Lehmann said.
“It was really nice to see him make runs in the middle but no (it’s not locked in).
“We’re going to be pretty versatile at this tournament. I think that’s one of our advantages, we have batsmen that can float and move (up and down the order).”
It could potentially be mind games from the coach, with Australia’s World T20 campaign in India starting next Friday against New Zealand.
They face West Indies in a warm-up game on Sunday at Kolkata before shifting to Dharamsala for the trans-Tasman clash.
Regardless of whether Warner opens or not, Lehmann will have to leave one of Shane Watson, Aaron Finch and Usman Khawaja on the sidelines.
The no-nonsense mentor noted it would be a tough decision but far from unprecedented.
“You’ve got a 15-man squad and you have to leave four blokes out of the side. That’s always the hardest thing in World Cups,” Lehmann said.
“We had the same problem in the one-day World Cup last year.
“We had a captain one game and then obviously George Bailey didn’t play when Michael came back.
“They’re very, very tough decisions but we’ve got a squad mentality .. players understand that. We’ve just got to be really clear with them and it’ll be fine.”
Mitchell Starc, who is recovering from ankle surgery, headlines the list of Australian players currently unavailable.
“We’d love to have Mitchell Starc here but we haven’t got him. Other teams are missing important players too,” Lehmann said.
The squad departed Cape Town on Thursday, with no lingering fitness concerns.
Watson bowled in the Newlands decider, confirming he is fully fit, while Finch, James Faulkner and Nathan Coulter-Nile have also recovered from their respective injuries.
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