Warner managed just 34 runs besides his 61 at Headingley, which is the lowest total ever from an opener in a 10-innings series.
"He had a poor series against England no doubt, that's a fact, he knows that," Langer was quoted as saying by www.cricket.com.au.
"But he also hasn't lost his talent, because he was the highest run-scorer in the World Cup two weeks before the Ashes started, and he was the highest run-scorer in the IPL before that. The other thing about David Warner my experience tells me you never write off champion players. He's a champion player.
"He's going to have to keep performing, he knows that, but I'll be very surprised if he doesn't do well in the next few rounds of Sheffield Shield cricket, does well in the T20 stuff (for Australia), gets his mojo and confidence back, and hopefully he'll be raring to go for the summer," he added.
Warner bounced back to first-class form at first attempt in the Shield, posting 125 against Queensland off 221 balls, his innings laced with 18 fours before Test teammate Marnus Labuschagne trapped him in front.