The 29-year-old, who joined the Saints during the summer transfer window, scored 23 minutes into his first Italy appearance as the Azzurri moved up to second place in Group H with a 1-0 win over Malta.
Pelle claimed after the game that he deserved his chance to impress sooner, sentiments with which Vader agrees.
"I'm sure Graziano will continue to do great things and I am really happy for him," the Feyenoord chief told Sky Sports News. "It's great that he's now getting what he deserves by scoring on his debut against Italy this week.
"I also happen to think that he should have got his debut long before that but who am I to talk about Italy, they have such a great history in football.
"With him up front you can have the whole team play better. You can have the midfielders move up the pitch and you can have the wingers looking for space and I think that's his best quality - he can make the whole team play better."
Pelle has made nine appearances in all competitions for Southampton so far this season.