Low selected Bayer Leverkusen winger Julian Brandt ahead of Sane, who registered 14 goals and 19 assists for Manchester City last season.
"Forget it," Ballack told the Evening Standard. "I can't explain that. For me there is no photo finish. I can't see it. There's 23 players in the squad, to say you only see him in the position Julian Brandt is playing - you have to have a fantasy to believe that.
"Brandt is a good, talented player. He made his improvements this year. But he didn't play on the level that Leroy Sane played. Sane was at a bigger club, with bigger expectations, with better players.
"Nothing against Julian Brandt, but I can't explain why Low compared the two."
Sane's Manchester City teammate Ilkay Gundogan made the team, as Germany look to build on their 2014 success in Brazil.