Players get struck on the helmet with increasing regularity these days, but three in 16 balls is extreme. Wagner is to be monitored for 48 hours, although did return to the bowling crease late today, to good effect.
The pugnacious Wagner - one hard-headed hombre who likes to take the short ball challenge on - might like to consider putting his hook shot in the cupboard for a while.
"It's never nice to see a team-mate get hit," opener Tom Latham said last night.
"The medical team are out there and they were assessing him and we've got to leave it in their hands. "He was fine and he's a pretty tough character, Neil."
Much of Wagner's value with the ball is taking on a short-pitched approach to unsettle batsmen. The numbers strongly suggest it works for him. The player acknowledged that if he's dishing it out he has to expect some back.
Mitchell Santner was also struck on his helmet by Taskin Ahmed, the ball glancing off as if - had he been playing another ball sport - Santner had steered a header into the bottom corner of the net.
Earlier Latham's 177 left him 23 shy of becoming the sixth New Zealand opener to score a double hundred, and it would have been the eighth occurrence.
Glenn Turner and Brendon McCullum did it twice, Bert Sutcliffe, Graham Dowling and Bryan Young once each. So was Latham chuffed or dismayed?
"Obviously as a batsman you always want more and never want to get out," he said.
"In the context of the match it was pretty pleasing to make a significant contribution to the side and just build partnerships with the top order.
"When you're behind chasing a big score you need partnerships and we managed to do that."
Latham was loath to put a number on a target New Zealand would be comfortable chasing tomorrow.
The first job is getting seven Bangladeshi wickets. They're not about to declare and give New Zealand a sniff. The wickets will have to be dug out.
"We like to play a winning brand of cricket and whatever the score is, hopefully it's a reasonable chase and we'll certainly be having a go at it."