Warner will return home from the tour of the UK after surprisingly being left out of the 15-man squad for Tuesday's one-day international against Scotland and the five-game series against England.
Insisting the decision was form-based and nothing to do with attitude or behaviour, Lehmann said Warner's recent lack of runs in the 50-over format made it a tough but necessary call.
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Few would argue the explosive batsman remains a match-winner when at his best but Lehmann wants consistency to form the backbone of a winning culture.
"Guys who are consistent are going to play for the team and Dave's just had some poor form and not high scores," Lehmann told AAP.
"In terms of his work ethic and the way he wants to play for the team, it's exceptional. We just want more runs on the board.
"At the end of the day, he hasn't made enough runs in this format of the game.
"He knows that but we expect more runs from a player of his skill level and how many chances do you get I suppose?
"Obviously he's had a few and now it's a case of him going back to (domestic one-day cricket) and getting a few runs in that and getting back into the one-day team."
Warner was dropped despite top scoring for Australia with 53 in a 29-run Twenty20 loss to England at Chester-le-Street on Saturday.
The 26-year-old scored nine against England in his only ODI appearance in June's ICC Champions Trophy, before being suspended from the rest of the tournament following his altercation with England batsman Joe Root in a bar.
Warner played in three games against Sri Lanka in the Australian summer - with scores of 4, 60 and 10 - and had largely disappointing one-day campaigns in England and the UAE last year.
Lehmann said Warner was disappointed but accepting of the decision and stressed he had been impressed with his attitude.
"He's been exceptional off the field and the way he's handled himself, considering he's copped a fair bit at the grounds. He should be proud of that," Lehmann said.