But back to No3. It's a specialist role, not to every batsman's taste.
New Zealand have had two highly successful players in the job in the past 30 years, John F. Reid and Andrew Jones. Lefthander Reid averaged 46.28 in 19 tests, almost exclusively at No3 but was gone by 30; Jones averaged 44.27 in 39 tests, and all but four of his innings - twice preceded by a nightwatchman, once batting at No4 and once opening - were in the first drop spot.
"The key thing is it's a really pivotal role, irrespective of who's doing the job," Edgar said.
"You could be facing the new ball very soon, fresh bowlers, fresh track, the ball could be swinging, pace is there, the bowlers are all fired up and certainly you're really challenged physically and mentally.
"It's [about] your ability to play a good line, what not to play, how to play the swinging ball, then being adaptable to the situation. You need to be a bit multiskilled in plan A or B, so it's about what your game plan is for various scenarios."
It's not to every batsman's liking, then again Jones had a strong aversion to opening - even though he might be walking out in the first over of a test.
Williamson is locked in at No3, and has an improving test average of 34.78 over 27 tests. In that last 13-test run, he has averaged 37.6.
So, assuming Williamson does not recover, what are the options?
Canterbury's Dean Brownlie, with 14 tests and an average of 29, is a possibility. He lost his test spot in Bangladesh to the allround skills of Anderson. He has been at No3 in his province's two Plunket Shield games this season, perhaps as a dry run, and produced 37, 17, 51 and 1.
Martin Guptill, back from a double injury break, hit 85 opening against Canterbury this month.
Jesse Ryder, with two Plunket Shield centuries in as many matches for Otago, had earlier been ruled out for the tests by Edgar, at least for now.
The minor injuries he picked up against Canterbury this week have had him withdraw from the warmup game against the West Indies at Lincoln next week, his provincial captain Derek de Boorder taking his spot.
Tom Latham is a chance, and there's another option. Aaron Redmond had a cracking season for Otago last summer. He has now hit 271 runs in four innings this season and knows the first-test venue as well as anyone. He opens the batting for the makeshift West Indies side at Lincoln.
Hesson rather hinted when Peter Fulton got his recall last summer that the selectors had decided to move on. Both had strong claims, but it was a case of one 34-year-old, not two. It may be time for a short-term rethink.
Test squad
• New Zealand's first test squad will be named next Friday.
• Regular No3 Kane Williamson is not expected to have recovered from a fractured thumb in time.
• The last time a Kiwi other than Williamson was batting at No3 in a test was in August 2012, 14 tests ago.
