Following five wins from their previous nine matches, and successive triumphs over Gold Coast and Melbourne, the Lions were horribly exposed by a physical and classy Crows outfit.
Adelaide won all the crucial statistical categories and kicked 13 goals to three after half-time to completely steamroll the home team.
Leppitsch said it appeared as if the Lions were resigned to the result a little too early.
"It did feel that way a little bit from the outside, didn't it? We were hoping the last 10 minutes would (wind) down itself, but that's not what happens in games of footy, you have to fight them out," Leppitsch said.
"And we made some really poor skill errors that gave them goals as well, which made the scoreboard blow out even more."
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It was a brutal reality check for a team that had made great strides since their first bye following round nine.
Leppitsch said they were "bullied" in contested possessions and "killed" at the stoppages, and the numbers did not lie.
Adelaide won the contested possession count 153-122, the clearances 47-30 and the tackle count 61-46, despite having more disposals (378-357).
The Lions also conceded 43 scoring shots from 63 Adelaide forward 50 entries, which was a major concern for Leppitsch.
"We're going to have games where our energy level dips, but we can't have our competitive nature drop as well, that was probably the most disappointing part," he said.
"We always knew this last month was going to be tough because we're playing all finals contenders and those that are entrenched in the finals.
"That's going to be the next leg of our journey, to compete and compete well and remain in the game for longer."
