Rangers are now level on points with Celtic after a dismal start to the campaign under Russell Martin.
Both teams trail Hearts by six points, but now under the guidance of Danny Rohl, the Ibrox club have strung together a level of consistency that has quietly pushed them back into title contention.
During a three-year spell at Ibrox, Defoe clinched the Scottish Premiership title when Steven Gerrard was manager, and the former England forward believes the latest Old Firm result is “huge” for his old team.
“This win is a massive win because both clubs have had their struggles,” he said.
“And now they’re both level on points. Rangers winning this game and how they won, this is huge.
“Not just for the players but for everyone involved in the football club, and the fans. It’s one of the biggest games in world football.”
It is a sentiment echoed by Ibrox centre-half John Souttar, who told Rangers TV: “I think we have experience in the squad and you have to help the younger boys.
“The atmosphere can be intimidating for some lads, but we didn’t show it today. Everyone stood up and took the ball and aggression off the ball was massive.
“We have momentum, athleticism, speed and power and when we do that and press high and put them under pressure then we have a great chance to win and we did that.”
And Souttar added: “The supporters were amazing. Some of my family were here and it was incredible.
“It is a special moment for everyone here, but we want to make sure there are more of these in the months and years to come.
“We have to build on this. We have to keep the momentum building and do the basics and what the manager wants from us and then we can see where we go.”