New Zealand had produced 'almost the perfect performance' to destroy England in a World Cup match that lasted less than 50 overs on Friday.
Southee took a New Zealand best 7-33 that bowled England out for 123 in 33.2 overs in their Pool A clash at Wellington Regional Stadium, before captain Brendon McCullum sealed the eight-wicket win with a blistering attack on England's bowling.
"It was a pretty amazing day when you think back on it. It's almost the perfect performance," Southee said of New Zealand achieving the 124 needed for victory in 12.2 overs.
"One of those days almost (where) we can't do anything wrong.
"You take the personal accolades," he added of his man of the match performance. "But I think it's just credit to the way we've bowled as a group.
"I guess today was one of those days where I got the rewards and I'm sure there'll be another time we will bowl just as well and someone else will take the rewards."
Southee's personal haul, which bettered the 6-19 current bowling coach Shane Bond had held for 10 years, was supported by the team's efforts in the field as well as his fellow bowlers.
New Zealand threw themselves around in an attempt to save runs left, right and centre, while Daniel Vettori created scoreboard pressure that was rewarded when Adam Milne typified the fielding effort with a diving catch in the outfield.
Southee's ability to produce outswing to the right-handed batsmen, however, was key in his demolition job on Friday.
While the ball was not 'hooping around' in brilliant sunshine it was that late swing away from the batsmen that did for five of the seven wickets - all right handers.
Ian Bell, James Taylor and Chris Woakes were all bowled by late-swinging deliveries, while Jos Buttler and Steven Finn were caught behind the wicket from deliveries that shaped away.
"There wasn't a hell of a lot in the pitch and I think we saw that with the toss," Southee said of the fact England's Eoin Morgan had chosen to bat, while Brendon McCullum said he would have done the same had he won the toss.
"It looked a good batting wicket but we managed to get it swinging and if anyone can get it swinging then it's a different ball game.
"It hasn't swung like that in a one-day game for a while and for the old ball still to swing, I think it just proved the difference."