One of Sergio Perez's former team chiefs has slammed the Mexican driver.
Peter Mucke is a well-known name in the formative classes of motor racing, having paved the road to F1 for stars including Sebastian Vettel, Robert Kubica and many others.
In 2006, Mucke ran Perez - now with Force India - in Formula BMW.
"Already then, Sergio showed that he has talent. That is beyond dispute," he told the German-language Spox publication.
"But his approach was totally unprofessional. I've rarely worked with a slob like him. His apartment in Berlin looked like a battlefield. He wrecked my rental car when he came home drunk from a party. He did everything you cannot do.
"Always in the background was his Mexican sponsor," said Peter Mucke, referring to Perez's ongoing backing by Carlos Slim and Telmex.
"Sergio didn't need to worry that the money would end -- he knew it would keep coming. That was the key. He never would have reached the top if not for that money. With his talent alone, he would have been out after that one year in BMW."
Peter Mucke said the antithesis to Perez's approach was the one taken by Sebastian Vettel, who also drove for the Berlin-based junior outfit.
"Definitely. He was very different," he said, referring to the quadruple world champion and Ferrari driver.
"If the day starts at 8am, some drivers are rubbing sleep from their eyes at 8.05. But Seb was always up at 6, has jogged for half an hour and has his head in gear at your door. And I didn't tell him, it was all his own initiative. That makes all the difference," Mucke added.