The former Blues defender has described the feeling of lifting the famous, old trophy at Wembley in 2008 as 'priceless'.
And Johnson has also outlined how he quelled the threat of Cristiano Ronaldo on the road to the home of football, in the never-to-be-forgotten quarter-final win over Manchester United.
The former Chelsea and Liverpool man was a key component of Harry Redknapp’s side, as they ended the 69-year wait for Pompey to lift the famous, old trophy.
It was the only time Johnson was to do so, making for a very special achievement in the former England international’s career.
Johnson told Planet Football: ‘To actually hear that whistle, knowing that you’ve done it, it’s impossible to bottle up.
‘If you could bottle it (that feeling), it’d be priceless. It’s one of those moments when you’re thinking of a hundred things in milliseconds.
‘Even telling you now makes my hair stand up. It’s one of those moments no one can ever take away from you.'
The key to success in 2008 came in dispatching Manchester United at Old Trafford in the quarter-finals, with the champions and eventual Champions League winners at their fearsome best under Sir Alex Ferguson.
United included the likes of Carlo Tevez, Wayne Rooney and Rio Ferdinand in their side, with Johnson detailed to keep a certain Ronaldo quiet.
He added: ‘To be fair, we were just enjoying it. At the time, we were beating most sides, we were in a good league position, and we were just having fun.
‘United were favourites and rightly so. But we knew that if we went there with a game plan, which was just to be an obstruction to them, we had the players to deal with it.
‘He (Ronaldo) is a phenomenal player, but obviously I was a big lad and quick as well, so I wasn’t worried about getting close to him because if he wanted to have a race I could run, or if he wanted to be physical I could be physical.
‘I wanted to get as close as I could and try and have an impact when the ball arrives so that you unsettle him from the start. As we’ve all seen for many years, if he starts enjoying himself then everyone’s in trouble.’
Johnson was to make 100 appearances across three years at Fratton Park after arriving from Chelsea, initially on loan in 2006.
He would eventually move on to Liverpool for a whopping £18m, but revealed came close to making moves to Ajax and Lyon instead of coming to PO4.
Johnson added: ‘I believed that I could play that level (at Chelsea), but I wasn’t getting the game time I wanted and needed.
‘I was close to signing for Ajax and I was literally about to sign for Lyon and then I spoke to Harry funnily enough, and he was like, “You know what? Out of sight, out of mind.”
That was literally what he said.
‘If I’m playing in these other leagues, yes, I could do it, but then you could be missed a little bit. "Come and play for me, play every single week, you know you’re going to enjoy yourself”. Within 10 minutes I was sold. It was all about Harry, really.’
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