It was 1-1 against England when Southee, who'd had a taste of international cricket in T20s, was called in for the injured Kyle Mills.
With his 11th delivery he dismissed England captain Michael Vaughan; with his 17th he sent back Andrew Strauss. He finished with five for 55 on debut and, in a losing test, clobbered 77 not out off 40 balls with nine sixes.
"It was Stephen Fleming's last test," Southee said of the outgoing New Zealand skipper.
"He was someone I grew up idolising and being able to play in his last test was something special, and I'll never forget him presenting me with my black cap. A very proud moment."
Knowing he could compete at the highest level helped and things rolled along for a while.
But there were good quality rivals, such as Mills, Chris Martin and for a time Iain O'Brien, and Shane Bond. Southee, finding his international feet, came and went.
At Christchurch in an ODI in 2009, he was flogged for 105 in 10 overs as India rattled up 392 for four - "I bowled a shower" - and was discarded.
He quips that he's now got New Zealand's worst and best ODI figures, courtesy of seven for 33 when he poleaxed England in last summer's World Cup in Wellington.
Southee has no issue with his droppings, and there's been a couple. Southee's attitude is you can either knuckle down, or just roll along and not make full use of your ability.
"It was definitely justified. I wasn't performing to the level expected of a New Zealand cricketer," he said.
"I probably was not as fit as I should have been, probably a little overweight at times.
"You can blame everyone and feel you're hard done by, and say 'it's not my fault'."
But for the young man raised on the family farm at Waiotira, between Waipu and Whangarei, that wasn't the way.
"With the upbringing I had, that was not the attitude. I knew I wasn't working hard enough. Just being out of the side, you're watching games on TV and wishing you were there.
"That was a real motivation. I got a little fitter, and worked on my game.
"It was more a kick up the arse. I'd come in as a youngster, everything went pretty well for the first little while and then came crashing down pretty quickly."
He missed a Champions Trophy in South Africa, when New Zealand made the final, and a T20 World Cup.
In March 2012, Southee was out again, on the back of none for 140 against South Africa in Dunedin. His good mate, and now the world's sixth-ranked test bowler, Trent Boult, was axed too.
In came Brent Arnel and Mark Gillespie. Odd now, to think back. Again, no complaints. Five months on the sidelines. The turning point came at Bangalore, in August 2012. Southee was recalled and took seven for 64, still his best test figures.
Bangalore showed what he was capable of. He looks back and rates it perhaps his finest performance.
But here's the thing: New Zealand were well beaten. Southee, like his Northern Districts mate Kane Williamson, savours performances which help contribute to either success or, next best, preventing defeat.
His part in New Zealand's 167-run win in Ross Taylor's final test as captain in late 2012 resonates. Southee took eight wickets, Boult seven - "It's still one of my favourite test victories".
Southee's 10 wickets at Lord's, and a place on the cherished honours board, came in 2013 and, with left-armer Boult, he forms one of cricket's highest quality new ball partnerships.
When he's on song, his control and ability to beat the best batsmen around off stump is as good as any seamer in the game.
The New Zealand team has been relatively young for a while. Long gone are the people - Fleming, Vettori, Mills, Oram and Bond - Southee would see in the dressing room and remember it all as a bit of a dream.
Now he's one of the players the newcomers would look to for guidance. The only difference, when Southee was starting the equivalent figures were considerably older than he is now.
Coach Mike Hesson talks of Southee's influence among the leadership group. Williamson is expected to take over from Brendon McCullum, bowlers are rarely captains and Southee says that's fine by him.
"I'm pretty relaxed about that kind of stuff. We've got a strong group of leaders."
Among them, Southee has high praise for captain McCullum - "a fantastic leader". "He's done wonders for the team. He dragged us up from a place where it wasn't great. Him, Mike Hesson and the support staff have got us to where we are today."
The players have done their bit too, few more than the guy from the farm up north.
