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That means Australia are on the hunt for a No.6 batsman and Faulkner will need to bide his time.
"I suppose he's in that allround spot at the moment isn't he and Shane Watson's been doing that for us," Lehmann said.
"He's got to go back and make hundreds and take wickets and improve both skills as best he can.
"I think with the conditions you wouldn't do it in Australia... you might do it somewhere like Adelaide or Sydney ... but (most likely) we'll have six batters."
Faulkner was picked at The Oval partly to take the heat off an injury-hampered Watson and also to send a message to the likes of Phil Hughes and Usman Khawaja that sub-par performances wouldn't be tolerated.
Australia had faith that Faulkner's aggression and competitiveness would see him step up to the mark, and the 23-year-old delivered.
At least now Australia know they have a talented young player in the wings who isn't overawed by the big stage.
"I was really impressed with his debut," Lehmann said.
"He got in their face and actually had a crack. I was really pleased with that. He took four (first innings wickets) and played the game we wanted to play at the back end of our innings with the bat."
Watson scored his first hundred in three years and looks set to bat at No.3 in the return series.
Australia will be hoping the competition presented by Faulkner will also bring the best out of 32-year-old Watson.
The star allrounder had a disappointing series overall, but Lehmann said Watson wasn't far away from having an "Ian Bell-like series".
"He'd like to perform better but I think he ended up averaging 43 so he had a lot of starts," he said.
"The last two he's played he's made a start and gone on with it."
Lehmann said Australia needed to develop a "learning to win" attitude.
He admitted Khawaja and Hughes face a tough road back, and said the batting line-up selectors choose for the first Test at the Gabba will be given an extended chance.
"When we get our side for the first Test match, the batting seven will be the side for the first couple I would think at least," he said.
"We'll be pretty settled in Australia knowing the conditions really well.
"Early season Shield form will count and a couple of tour games against England sides and how certain players played on the Australia A tour.
"(We need to) get the right mix of players to compete against England and play the brand we want to play."