Louis van Gaal has criticised his former Manchester United players, describing them as "unprofessional" for refusing to read his emails.
The former Netherlands manager spent two seasons in charge at Old Trafford, but was sacked and replaced by Jose Mourinho in May 2016, just two days after leading the club to their first FA Cup trophy in 12 years.
Van Gaal revealed he used to have individual meetings with players to track their progress, but admits they would often ignore his messages preparing them for the session - forcing him to track when they had been read.
"I developed the digital tracker with my IT man. Each player was able to log in," Van Gaal told 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 responding to emails, he said: "That's true, too. But this testifies to their lack of professionalism 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 also heaped huge praise on Bayern Munich striker Robert Lewandowski, claiming he tried to bring the Poland international to United.
"He is currently the best striker in the world. I also wanted to train Lewandowski and wanted to bring him to Manchester United," Van Gaal added.
"The price was not a problem for Manchester United, but Bayern did not want to let him go."