Bayern Munich doctor Hans-Wilhelm Muller-Wohlfahrt has said former coach Pep Guardiola is "a person with low self-esteem, who will do everything to hide it from others."
Muller-Wohlfahrt, 75, left his role as Bayern's club doctor after 38 years in the aftermath of a Champions League quarterfinal first leg defeat in Porto in 2015 following disagreements with Guardiola. He has since returned for a third spell at the club, which he described as being "like a family."
In his autobiography, being serialised in Bild, Muller-Wohlfahrt wrote that "his sense of honour" had been hurt by Guardiola, Bayern coach between 2013-16.
He said he was "verbally attacked while the players were receiving treatment" and was "blamed for the numerous injuries, the physical condition of the players and ultimately for the defeat" in Portugal.
The Bild extract said Guardiola had said: "It cannot be that injuries here last six weeks, but in Spain only a fortnight."
Muller-Wohlfahrt said the coach "was upset every time a player had to come off with a muscle injury" and told him they should play on.
"I consider Pep Guardiola a person with a low self-esteem, who will do everything to hide it from others," Muller-Wohlfahrt wrote.
"He seems to live in constant fear of losing power and authority, rather than defeats."
Muller-Wohlfahrt accused Guardiola of "turning back the clock" at Bayern and "turning upside down our well thought-out, tried and trusted medical preparation programme."
The doctor claimed Guardiola was always "reproachful and indignant" when it came to injured players, adding: "He knew everything better."
He said Guardiola "wasn't interested at all in medical matters," but "expected medical wonders from us."
In the Bild extracts, Bayern president Uli Hoeness said he believed he could have prevented the falling out.
"If I hadn't been impeded [Hoeness was serving time in prison for tax evasion] I could have intervened in the conflict between Mull and Pep Guardiola," he said.
"Pep Guardiola is a very proud Catalan, and Spanish coaches have a totally different relationship with their club's medical department.
"Muller-Wohlfahrt, on the other hand, is a very proud doctor who doesn't like discussing his very successful treatment methods.
"Two fronts collided full on in the spring of 2015. I was missing as a mediator. After defeats, similar scenes often followed like after the 3-1 loss in Porto -- a lot more often that you imagine.
"A reason why Bayern Munich has become so successful is because of its exceptional medical department which Muller-Wohlfahrt was, and is responsible for again now. The club owes him a great deal."
Muller-Wohlfahrt had also briefly left in 2008 following a dispute with then coach Jurgen Klinsmann before returning the following year after Jupp Heynckes, now in charge again, had taken over.