Lehmann said: "I have never taken such a woeful first touch in my entire career. I first wanted to play the ball out to my left. However, I changed my mind midway through.
"If that is the way the season begins for me, it can only get better."
Lehmann's cock-up stunned Germany coach Joachim Low, who was watching on TV.
He said: "A goalkeeper of Jens' class will commit a blunder like that only once or twice in his entire career."