The record haul helped United to a 7-1 win over Blackburn, which swept them to the top of the table for the first time this season.
And for Berbatov, it provided the perfect confidence boost after he did not even make the squad for last weekend's triumph over Wigan.
"It was a fantastic achievement," said Ferguson. "He could have scored six too because Paul Robinson made a fantastic save near the end.
"When strikers are not scoring they don't think they are doing their job right. That has always been the case. Today it came back."
Berbatov follows former United striker Andy Cole, Alan Shearer and Jermain Defoe as men who have netted five in a game since the new league was formed in 1992.
Source: Manchester Evening News