The German FA took to Twitter on Sunday to express their distaste over Joe Bennett's horror challenge on Leroy Sane.
The Cardiff defender was only booked for a dangerous tackle in the second-half of his side's 2-0 defeat against Manchester City.
And he was condemned for the challenge after the game, with the German FA adding to the dissenting voices.
They referenced this summer's World Cup, a tournament Sane would be in danger of missing had he been seriously injured by Bennett.
"Hey, Cardiff City Just letting you know, we have a really important tournament in the summer. Please don't hurt our players. Thanks," read the Tweet.
The Tweet was later deleted, while Bennett apologised for the challenge on social media.
"Just want to apologise to Leroy Sane for my tackle today," he wrote. "I tried to stop the counter attack and completely mistimed my attempt.
"I didn't mean to catch him like I did. I hope it's nothing serious and he recovers quickly."
Sane could still be out for up to a month following the tackle, and Pep Guardiola insisted after the game that players must be better protected by referees.
"For football in general players are the artists. The only thing they can do is protect them," said the Catalan coach - quoted by BBC Sport.
"Referees have to protect - not just mine, all players. Sane will be out for a while. Maybe two or three weeks, or a month, we will see tomorrow. It's his ankle.
"I know my players, because it's not just one, there was many. They decided to play in that way. There is one man who has to decide what is correct and what is incorrect. If he doesn't anything can happen."