Former Manchester United boss Louis van Gaal has taken fresh aim at the players.
Van Gaal's strict approach saw him send personal e-mails to players ahead of upcoming meetings - however some members of his squad pretended they had read them.
"I developed the digital tracker with my IT man. Each player was able to log in," he told Bild.
"So I gave everyone the opportunity to prepare for the conversation with me at home and to meet me in dialogue at eye level."
Asked about players attempting to dupe the system and pretend they had read the messages, he said: "That's true, too. But this testifies to their unprofessionalism and I have then addressed them. "