The 34-year-old scored the opening goal for the Three Lions in Sunday's 2-0 World Cup qualifying victory over Lithuania.
It was the Sunderland striker's first appearance for his country since November 2013 but he showed he still has a predatory instinct at international level with a typically well-taken goal.
Defoe was part of the England squad which underperformed at the 2010 World Cup in South Africa, although he did hit the winner in the game against Slovenia.
At that time Lallana was preparing for a League One promotion push with Southampton but his memories of Defoe stretch back even further than that.
"When you look at it like that it is crazy but it is nice," he said.
"He thoroughly deserves to be playing on an international stage and at this level and he proved today what he is about.
"It still feels like you are playing with a 25-year-old Jermain Defoe. My dad used to take me to watch Bournemouth play when he famously scored in 10 games in a row.
"To be playing with him for England is quite surreal. It is the Jermain Defoe of old. You bet your bottom dollar he is going to score a goal and he did."
With the three points moving England closer to qualification, Southgate has left the door open for Defoe to make his squad for the World Cup next summer.
And Lallana did not downplay the influence the former West Ham, Tottenham and Portsmouth forward could have in Russia.
"Of course you can't win things with just kids and inexperience and it is great to have someone like that around the camp," he added.
"It is refreshing to see the hunger he still has, at times you think he is 23, 24 because he is that hungry and that driven to still improve.
"His enthusiasm for the game is really refreshing and it is great for people in our squad to see.
"We have got a lot of young players so it is great to see the hunger he has still got.
"He is determined to not just be here for this squad, keep being picked and be in the squad for Russia at the World Cup - and why not when he comes and contributes like he did (against Lithuania)?"
England have managed just seven goals in their last nine games in major tournament finals, and Liverpool midfielder Lallana reckons Defoe could help to improve that tally.
"It can be massive," he said when asked how beneficial it could be to have a natural goalscorer in a potential World Cup squad.
"He is all about goals but I think his link-up play at times was superb. He wants to be in the six-yard box and feed off scraps at times and you need these type of players so I was delighted for him to get his goal and get us on the way for three points.
"He is a great role model for everyone in the squad. He has been absolutely brilliant this week, he sets a great example for a lot of us players."
Additional reporting from PA