Ex-Manchester United manager Louis van Gaal has claimed many of his former players were “unprofessional” during his time at the club, citing their failure to acknowledge his feedback.

The Dutchman would send personal emails to his players detailing their progress ahead of face-to-face meetings but attached alerts to the messages meaning he could see whether or not the emails had been opened.

The 66-year-old concedes that a number of players didn't bother to read his feedback.

“I developed the digital tracker with my IT man. Each player was able to log in,” Van Gaal revealed in an interview with German publication 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.”

When asked about players not bothering to read his messages, Van Gaal said: “That’s true, too. But this testifies to their unprofessionalism and I have then addressed them.

“But I already did that with the emails at Bayern. My conviction is that a full professional also wants to live professionally. Like Arjen Robben. He read the emails.”

Van Gaal spent two years at Old Trafford before his contract was cut short by the club in May 2016.