The hosts drew the third Test in Melbourne on Tuesday to reclaim the Border-Gavaskar Trophy, but Lehmann said dropped catches in India's first innings cost his team dearly.
Australia set the tourists a 384-run victory target off just 70 overs, but India hung on to be 174 for six when both captains called the match off with four overs left.
Lehmann was upset by a series of spilled catches in India's first innings which enabled the tourists to restrict the first innings deficit to 65 runs.
Australia dropped three catches with spinner Nathan Lyon bungling a regulation two-handed head-high chance off his own bowling when Ajinkya Rahane was on 70. He went on to make 147.
Shane Watson put down Virat Kohli (88) at first slip off Mitchell Johnson and the vice-captain went on to score 169, while substitute fielder Peter Siddle dropped a two-handed chance off Lokesh Rahul, although the debutant was out off Lyon's next ball.
"Shoddy at best," Lehmann told reporters. "We've done a lot of work and I can't complain about the work ethic from the lads, but the big ones that cost us were the first innings.
"We dropped Kohli and Rahane and that cost us dearly in the back end of the game. Catches win matches."
Lehmann said Australia's drops in the field were not down to a lack of practice under fielding coach Greg Blewett, but rather confidence.
"It's not volume or practice, they're very good at that," he said.
"It's probably more confidence to be honest, I've been really pleased with the work ethic. They're catching brilliantly in practice."
Lehmann said former Test batsman Blewett had been working the players hard in fielding drills to get an improvement.
"He's done a really good job. (Injured skipper) Michael Clarke said he's worked the boys as hard as we've ever seen anyone work them before," the coach said.
"We missed a couple of run-outs we should have taken as well," he added.
Lehmann said the addition of Ashton Agar to the squad for the Sydney Test was to give more spinning options if needed.
"He's a left-arm spinner to take it away from the right-handers and depending on what we get in Sydney," he said.
"Traditionally the SCG has spun, last year it seamed, so just to give us some cover really.
"If it spins then we want the two options for the captain and then we'll have to work out what we do with the bowling attack from there. But we've got to get 20 wickets."
Agar, who scored a memorable 98 in his Test debut against England, could possibly bowl in tandem with front-line spinner Lyon at the SCG.
The Australia squad is otherwise unchanged, with all-rounder Mitchell Marsh still ruled out with a hamstring injury.
The Sydney Test gets under way on Tuesday, January 6.
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