Rooney has been in phenomenal form for Manchester United this season and took his tally to 32 goals with another brace in Sunday's 3-0 win over Fulham at Old Trafford.
It took United back to the Premier League summit and once again led to a glut of plaudits for the 24-year-old, who it is now generally accepted has gatecrashed the trio of Lionel Messi, Cristiano Ronaldo and Kaka who were regarded as the best three players on the planet.
Having worked alongside him at close quarters since his own club record £30.75 million move from Tottenham in 2008, Berbatov knows exactly how good Rooney is.
And the Bulgarian has no hesitation in declaring the striker his number one.
"At the moment, he is the best in the world," said Berbatov.
"He is still so young and has the chance to be even greater."