Pakistan won the toss and elected to bat against New Zealand in the second one-day cricket global at Saxton Oval on Tuesday.
Meanwhile, Guptill has downplayed his back injury after guiding New Zealand to an eight-wicket win in the rain-interrupted second ODI against Pakistan.
The Black Caps are playing a five-match ODI series with Pakistan, with game three in Dunedin on Saturday.
However, not long after, he was walking back to the pavilion as he was caught by Astle at deep midwicket off the bowling of Southee for a career-best 51, which came off 31 balls and included four boundaries and four sixes.
On the other side, Guptill and Munro started to bat for New Zealand where in 1 run Munro was gone and in 47 runs captain Williamson was gone as well. The sixes were hit at will for Guptill - five of them in total - while Ross Taylor provided suitable support.
Mohammad Hafeez's steady 60 off 71 had anchored the Pakistan innings, but he disappeared early in the 32nd over and the visitors looked in all sorts of trouble at 127-6. In the third over, Pakistan unsuccessfully reviewed an LBW decision against Kane Williamson (19).More news: Breathtaking video shows group of alligators surviving frozen NC river
Having restricted oppositions to manageable scores all through their recent golden run, Pakistan were let down by their bowlers in Wellington.
The game was evenly poised when Guptill and Taylor ran for shelter in the 14th over but the experienced pair made a mockery of the run chase, with Guptill reaching his 33rd half century in a game-high 87 from 72 while Taylor chipped in with 44.
All five regular bowlers chipped in with wickets, and it was left to Pakistan's lower order to respond with a magnificent rearguard action as half-centuries from Hasan and Shadab took Pakistan - once tottering at 141 for 7 - to a more presentable 246. Babar Azam couldn't have offered an easier catch to first-slip, helping Lockie Ferguson open his account.
Amir and Ashraf claimed one wicket each.
Sarfraz Ahmed was stumped on three when he went down the wicket to Astle, and Hafeez lost his wicket dancing down the pitch to Mitchell Santner.
The innings looked to be petering out well under 200, and it took a whirlwind partnership between Shadab and No. 9 Hasan to restore some competitiveness to the contest.