And the Southampton boss heaped praise on Pompey fans for sticking with their side all the way despite falling to a 4-0 defeat.
The Blues were put to the sword against their fierce rivals in the third round of the Carabao Cup.
Kenny Jackett’s men had their opportunities in the opening 20 minutes but were punished for not taking them.
Danny Ings’ clinical finishing put the Premier League outfit 2-0 up at half-time before Cedric and Nathan Redmond netted after the interval.
However, the Fratton faithful continued to back Pompey until the final whistle, while visiting supporters made their share of noise.
It was Hasenhuttl's first experience of the south-coast derby – and revealed it was one of the best games he’s been involved in.
The St Mary’s boss said: ‘It’s unbelievable. I must also say they didn’t stop singing after being four down.
'You could feel the tradition that is in this derby.
‘I think I have never had such an atmosphere in a stadium so far and I have seen a lot in my entire footballing career.
‘It was a very special game for me also.
‘I was hoping it is coming in a way that you can also celebrate the football and if you see such a game here then you know why football is so popular in England.
‘It is exactly what it is. A little bit raining. A fighting game and an unbelievable crowd that never stopped singing.
‘If you think about English football then that for me is English football.’
It could have been a different story had Pompey made their pressure count in the early stages.
John Marquis struck the post, Brett Pitman had two efforts saved and Christian Burgess hooked a shot wide.
Ings’ 21st-minute opener was a sucker-punch for Jackett’s men before the striker doubled his tally on 44 minutes.
Hasenhuttl still thought the Blues still could have got back into the game – but knew Cedric’s strike with 13 minutes remaining put the tie beyond reach.
He added: ‘We really didn’t start well in this game but the players knew they had to fight for every inch and after the 1-0 it was a much better game for our side.
‘After the 2-0 I was not sure if this game is done for us so you never know if they make the 1-2 then suddenly everything is alive again and it gets difficult for you. At 3-0 you know it is done.
‘It was a hard job to do but the guys did it well.’