"There's been times where I've been getting up early and doing some running and think... 'Geez, I'd love to be still playing.'"
But mostly, it is the aggressive drive that he misses.
"Competing. And sometimes as a halfback, getting targeted defensively. And then sometimes there is words said between you and the opposition back-rower or centre, and then it becomes personal. Then it's like, 'Well come on then, let's go.' That sort of competitiveness, that's what you miss."
While he knows it is too late now to ever make it back onto the big stage, Johns still lets himself dream of the idea of being back out there.
"When you retire initially, the first four or five years there's no dramas, by the time you are in your early 30s, you are cooked," he said.
"You're gone. You're head is gone and your body ... well my body was shot. So I knew it was time to go. But then after a while you start sort of bulls***ing yourself saying, 'I reckon I could still maybe ... '"
The last time Johns attempted a comeback of sorts, it didn't go too well.
The former Newcastle playmaker, along with Sydney Roosters great Brad Fittler, had entered the World Rugby Classic in 2012 - a rugby union event for former greats of the game in Bermuda.
Considering it was five years after Johns had retired from professional football, he didn't expect the tournament to be quite so serious, hence his rather relaxed attitude in the days prior.
"I went away to play a rugby union thing in Bermuda," Johns said.
"We won it. And we beat South Africa. So I thought it was just like a hit and giggle. We go over to Bermuda, I've bendered for four days on the way over. Yeah, this may surprise you ... for five days.
"So we get there and it's full on contact. I haven't done it for six years. We are playing South Africa, against Bobby Skinstad, Percy Montgomery - the best ever South African players.
"So then we get on the field and the competitive juices come, and we are jamming blokes. That's where I did my neck, I had to get my neck fused after it."
Johns was quick to commend former Kangaroos captain Fittler for his performance at the Classic tournament, which he saw as indicative of the way he played his entire career.
"Freddy destroyed them. He absolutely destroyed them," Johns said.
"After the game the South Africans said: 'We know you guys. You (Freddy) could be earning a million dollars in Japan. If you played now in Japan.'
"He was unbelievable.
"The thing is with Freddy, that people underestimate, is just how tough he was.
"He had the sidestep and he was skilful, but he was one of the toughest players I'd ever played with.
"When we were playing Origin, going end to end, Freddy would just get the ball and charge into the opposition, trying to get you out of trouble. It would just lift the whole team - that's what stood out to me about Freddy's career."
