But Ajaz Patel has yet to take a single wicket in his three opportunities in NZ.
Santner keeps it tight, builds pressure, gives the quicks a rest and picks up the odd wicket.
Our pace bowlers average 25 in the second innings of matches where Santner has played, and average 31.84 when he isn't playing.
That can be the difference between winning and losing.
However in the last 3 home seasons, he's averaged 29 with an economy rate below 2, while he averaged 38.4 with an economy rate of 2.5 before that.
He's bowled roughly 600 deliveries in home tests in the past 3 seasons. that's not enough to really talk about the probability of rare events like wickets reliably.
Ajaz Patel has shown that he has been able to build some pressure, so there's a chance that that led to this decision.
I was quite outspoken at the start of that tour that I did not think Santner should have been picked to play in Australia, as the conditions do not suit his style of bolwing.
But Santner has averaged 25.75 with an economy rate of 2.05.
There's no evidence from domestic cricket to support Patel over Santner.
Pretty short list, huh?