Mixed emotions for Southee
The 20-year-old was happy to be back in the limited overs saddle for the Black Caps, but says the end result was less than ideal.
Shahid Afridi hit an aggressive 70 off 50 balls and took two wickets as Pakistan recovered from a shaky start to post an imposing 287 for nine on a slow pitch.
In reply, New Zealand crumpled to be all out for 149 in the 40th over.
Southee opened the bowling with Shane Bond after Pakistan won the toss, and the Black Caps made the best possible start, Bond picking up the wickets of Salman Butt and Younis Khan without a run on the board.
But the Pakistanis regained momentum, Afridi's innings supplemented by Kamran Akmal's undefeated 43-ball 67 and Khalid Latif's 64.
Chasing a daunting target, New Zealand were never on course as Umar Gul shook them by bowling Brendon McCullum for 21 and Martin Guptill for four by the 10th over.
Aaron Redmond, 52, and Daniel Vettori, 38, provided the only resistance during a 69-run fifth wicket stand before five wickets fell for 10 runs.
Southee picked up 1-54 off his 10 overs in his first one-day outing for the Black Caps in nearly eight months, and managed just a single with bat before becoming the final New Zealand wicket to fall.
"It was a disappointing result, but it started off probably as good as any game," Southee told NZPA today.
"We had them two down early on, but then they just managed to put a few partnerships together and get through to 290-odd.
"At about 16 overs they were only on around 40 runs. We got off to a great start, but we just didn't keep the pressure on and take full advantage of the position we'd got ourselves into."
Southee has experienced a dizzying series of highs and lows since his first test for New Zealand against England in March last year.
He made an outstanding debut for the Black Caps, slamming an unbeaten 77 off 40 balls in the third test after earlier picking up 5-55.
Just over six months later, Southee was harassing the Australian top order in the first test in Brisbane. His four for 63 off 18 overs included the wickets of Matthew Hayden, Simon Katich and captain Ricky Ponting.
But his confidence took a knock later in the season when he recorded figures of 0-105 off 10 overs against India in early March in the third one-dayer in Christchurch.
Southee returned to test cricket for the third and final cricket test against India in Wellington later that month, then travelled to Australia for a mid-year stint with the New Zealand Emerging team.
Back in the Black Caps one-day team, Southee is working hard to erase the memory of his blow-out against India, which earned the dubious distinction of being the costliest 10-over spell ever delivered by a New Zealand ODI bowler.
"The last one-dayer I had was a bit disappointing, so it's great to get back out there and play," he said.
Not that today's effort was entirely satisfactory, he added.
"It was a bit of a mixed bag ... I guess you could say it was okay. My first spell was reasonably good, but there's still plenty to work on."
The remaining two matches in the series will be played here on Friday and Monday, before the two teams move to Dubai for two Twenty20 internationals on November 12 and 13.