Raymond Verheijen, a leading Dutch coach, has taken to Twitter to label David Moyes' pre-season regime as "Jurassic Park", subsequently branding the United manager as a "dinosaur".
The controversial comments follow after United striker Robin van Persie suffered a minor injury during the Reds' tour of East Asia.
It was reported that the Dutchman was taken off as a precaution by Moyes in United's 3-2 defeat to Yokohama F Marinos on Tuesday, as the player was complaining of a tight thigh.
Verheijen, who has primarily spent time as a fitness coach for clubs like Barcelona, Chelsea and Manchester City, was quick to blame Moyes for his fellow Dutchman's injury on Twitter.
"In Sydney Moyes said: 'We've overtrained Robin this week to build his fitness'. He picked up a muscle injury. It really makes you wonder how these prehistoric training methods can still take place at the highest level.
"All over the world in pre-season you see the pattern 'overtraining-fatigue-injuries'. Always avoid accumulation of fatigue in pre-season.
"But as long as most dinosaurs are still in denial & ignore how things develop in other countries, nothing will ever change in Jurassic Park. Obviously, players like RVP should learn to protect themselves better against 'overtraining' & 'punishing training'."
The former Wales assistant manager went further to suggest that Moyes' fitness coaches were clowns, who needed to be educated.
Verheijen has taken to Twitter several times to vent his anger and frustration at the training regimes of Premier League clubs, such as Arsenal and Tottenham Hotspur.
The outspoken Dutchman, who has also worked with the Netherlands, Russia and South Korea, appearing at three World Cups and three European Championships, has been critical of the newly appointed United manager.
When Moyes was appointed to succeed Sir Alex Ferguson on his retirement, the Dutchman took to Twitter in May to state: "The dinosaur of all dinosaurs get a 6 year (!) contract to manage one of the biggest clubs in the world. Only possible in Jurassic Park."
With all these dinosaur-related critical remarks, it is clear that Verheijen is preying on Moyes.
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