When he arrived in the middle, New Zealand needed 109 off the last 15 overs and things looked dicey. Pakistan were well up for it.
A few minutes later and the complexion had changed.
De Grandhomme, back in the team after bereavement leave, was a monster in the middle. He finished on 74 off 40 balls, sharing a 109-run stand off 65 balls with Henry Nicholls, who got to his half century just before the win was accomplished. There were 4.1 overs left at the end.
De Grandhomme clobbered five sixes and seven fours and destroyed the Pakistan attack.
"I just got told 'go and play your game'. Basically see the ball, hit the ball. Obviously it was my night, and 'Toey' led us through," de Grandhomme said.
"Toey" Nicholls, that is. His role was notable last night, too, a more considered contribution than the mayhem happening at the other end, but in its own way just as important, once captain Kane Williamson had been caught on the long on fence at a key juncture.
De Grandhomme admitted he is "feeling good in this team because as a team we're going really well. It does make life easier".
Nicholls, too, is having an important season and looking more settled in the batting group.
He played down the 11-match streak last night.
"It hasn't been talked about at all. One more game in Wellington is important and we just focus on doing what we have been doing.
"Whatever the records, it's just extra stuff for people to talk about."
Things could have been very different last night.
New Zealand had rattled along to 88 without loss, courtesy primarily of another rip-roaring assault from Colin Munro (56 off 42 balls).
But the classy young spinner Shadab Khan trimmed New Zealand's sails, as they lost four for 11 in 35 balls.
Shadab bowled beautifully. He was always going to be the key late on, but he too got collared by de Grandhomme. He wasn't alone.
The crowd were making a racket but de Grandhomme admitted, "I didn't really hear the crowd. I was just in the zone enjoying my time with 'Toey'."
Pakistan haven't played well on tour but coach Mickey Arthur said they had felt this would be their night - at least until de Grandhomme took guard.
"We were able to put New Zealand under pressure. But he [de Grandhomme] totally changed the game, the momentum," Arthur said.
"That was some serious hitting, he did play exceptionally well. It was really disappointing [for Pakistan]. We had tried to fight and fight and had it taken away at the end."
Meanwhile, allrounder Shoaib Malik is rated unlikely to be fit for Wellington on Friday. He has delayed concussion after being struck a nasty blow on the bare head by a return from Colin Munro.
Pakistan hope he'll be ready to return for the T20 series starting next week.
