Chelsea have endured a torrid start to the new Premier League season and sit in 12th place after nine games.
On Saturday, Jose Mourinho's side travel to Upton Park to face high flying West Ham United where Song is once again spending the season on loan from Barca.
The African star will not play any part in the match as he battles back to full fitness after a long-term injury.
'Two of the best players in the world'
“Cesc is one of the best midfielders in the world, he is a very clever guy," Song told whufc.com.
"When you give him room, he can give good final balls to the striker for them to finish.
“Pedro is an unbelievable player and one the best players in the world in his position.
"When I was in Barcelona I spent two years with him and he is a fantastic player.
"The way he plays, we have to be careful because he is very quick, he can turn left or right, he has good vision and he scores a lot of goals."
Word of warning
Song said Chelsea's bad start does not mean they have lost their star quality.
And he has warned his Hammers teammates they must be on their guard with the Stamford Bridge side getting back into the winning groove against Aston Villa last time out.
He added: "They won their last game at home and will come here trying to get a good result."
Song had been penciled in for his return to action against Chelsea with Hammers co-owner David Gold saying as recently as Sunday that he is 'ready to go'.
But he is still working on his fitness with West Ham having the luxury of not needing to rush him back given their superb start to the season and the array of midfield options available to Slaven Bilic.
Ironically Song could have been the ideal man to shackle Fabregas as he knows his game inside out having played with him at both Barca and Arsenal.