Berbatov became one of only four players alongside Andy Cole, Alan Shearer and Jermain Defoe to hit five goals in a game in Premier League history.
Asked whether it was good to have his strike partner back, Berbatov said: "Of course it's good. He's the type of player who knows how I play and I know how he plays.
"But we work hard in training. Sometimes you have days where everything happens."
Manager Alex Ferguson dropped Berbatov the previous Saturday against Wigan due to poor form.
Fergie said: "Strikers don't feel they're doing the job unless they're scoring. Dimitar's got it back."