Cristiano Ronaldo is the greatest player that Manchester United has ever had, according to Sir Alex Ferguson.

Ferguson is the former manager of Manchester United. He had managed the football club for more than 26 years, from 1986 to his retirement in May 2013.

Ronaldo was a player of Manchester United from 2003 to 2009.

"Cristiano Ronaldo was the most gifted player that I have ever managed," wrote Ferguson on his book titled My Autobiography. "Cristiano has exceeded all the other great players I have coached at Manchester United," Ferguson wrote.

Ronaldo was with Manchester United for six years before he signed with Real Madrid for a record-breaking £80 million transfer fee. Ronaldo's move to Real Madrid was definitely devastating for Ferguson. The Scottish manager even said once that he'd rather kill Ronald than let him go to Real. "I would rather shoot Ronaldo than sell him to Real," said Ferguson.

The new autobiography book of Ferguson is extremely anticipated because it gives the readers unparalleled insight into one of the most successful managers in the sports of football. The book was released on Thursday.

Aside from Ronaldo, Ferguson also talked about David Beckham's performance, following the loss of Manchester United to Arsenal in 2003. "As always, David was indifferent of my criticism," wrote Ferguson. "David swore and he was about 12 feet away from me," wrote Ferguson. "I came towards him and I accidentally knocked a boot, which hit David right above the eye, he tried to have a go at me and the other players just stopped him from doing so," wrote Ferguson. "I told him to sit down and that he has let his team down," Ferguson added.

"The next day, I called David and asked him to go through the video but he still would not accept his mistake," wrote Ferguson. "Those were the days that I told our board that David had to go," he wrote.

Ronaldo and Beckham were not the only footballers that Ferguson talked about in his autobiography. Ferguson's relationship with Roy Keane, Wayne Rooney and Rafael Benitez were also discussed in the said book.