What happens if Williamson

New Zealand’s top-six looks set in stone for the England cricket tests, but two nagging questions leap out.

Can the Black Caps captain and key batsman Kane Williamson defy a niggly hip injury to play all five tests against England and Australia in the next two months, and who replaces him if he can’t?

There appears some doubt over question one. Coach Gary Stead sounded more hopeful than bullish about his skipper’s fitness as he and co-selector Gavin Larsen prepare to name their squad on Friday for next Thursday’s first test.

‘‘I hope so. You never know, injuries can happen. We just have to manage him well and make sure his stretching regimes and all those things are going to plan,’’ Stead told Stuff.

Interviewed during Sky TV’S broadcast in Napier last Friday, Williamson described his hip injury as ‘‘an ongoing niggle’’, which restricted him to a solitary innings this season: 26 in 56 minutes for Northern Districts against Canterbury last month.

‘‘It comes and goes. It is settling, which is nice. A lot of [the last few months] has been rehab to get the hip right,’’ he said.

Having missed the five-match Twenty20 series as a precaution, Williamson goes in cold for five tough tests in just under seven weeks – two against England then three in Australia.

Interestingly, Stead said the longer Williamson bats, the less the injury bothers him. It appears diving or running in the field is the biggest concern as New Zealand hope to avoid the major setback of starting a test without their best player.

‘‘It’s not usually batting that aggravates it,’’ Stead said.

‘‘He’s been with us the last couple of games and had a number of red ball trainings with us as well. I’m reasonably confident he’ll be OK come the first test.’’

It brings Otago batsman Hamish Rutherford into the frame for potentially his first test in nearly five years, as the leading backup option.

Regular backup Will Young, still awaiting his test debut, remains sidelined until at least next month’s Twenty20 Super Smash after undergoing shoulder surgery.

Another leading top-order contender, Wellington’s South African run machine Devon Conway, doesn’t qualify for New Zealand selection until September.

That leaves Rutherford who will open for New Zealand A in

Friday’s three-day tour match against England in Whangarei. Now 30, Rutherford scored a memorable 171 on debut against England in 2013 but played the last of his 16 tests in January 2015.