Di Santo is on a half-season loan at Blackburn.
The 20-year-old has made three appearances since linking up with Rovers, but Big Sam expects the striker to return to Chelsea in January.
“Franco has contributed a huge amount,” said Allardyce.
“He could have gone on loan to a club in Europe, but Chelsea wanted to find out whether he is good enough for the Premier League.
“There’s no doubt that if he continues to play like he did on Saturday he will be great for us. Then perhaps Chelsea can benefit.”
