New Zealand retained injured Martin Guptill in their squad named Sunday for the upcoming Twenty20 series against Australia but have placed this season's breakout star, the uncapped Finn Allen, on standby.

A renowned big-hitting opener and a veteran of 94 internationals, the 34-year-old Guptill had a disappointing run of form in five matches against the West Indies and Pakistan in December when he averaged only 17.

In New Zealand's domestic competition his average was a low 11.5 before he missed the last two rounds with a hamstring injury while the 21-year-old Allen blazed away with 512 runs at an impressive 56.88.

New Zealand selector Gavin Larsen said the matches against number two-ranked Australia were "a significant step" in the build-up to the World Cup in India later this year and if Guptill fails a fitness test when the squad assembles in Christchurch on Friday he will be replaced.

"Martin's our incumbent opener and our highest T20 International run-scorer so we're backing him to do the job at the top of the order, but he will need to prove his fitness and it's good to know we have a ready replacement in Finn on stand-by," Larsen said.

"Finn's been in outstanding form and he's certainly an exciting talent."

There's a settled look to the remainder of the squad where wicketkeeper Tim Seifert will also open the batting with captain Kane Williamson at number three. 

Devon Conway, Glenn Phillips and Mark Chapman are set to continue in the middle order after strong starts to the international season. 

Trent Boult, Tim Southee, Kyle Jamieson and Hamish Bennett make up the pace-bowling quartet, with Mitchell Santner and Ish Sodhi the spinners and Jimmy Neesham the all-rounder. 

The opening match against Australia is in Christchurch on February 22. 

New Zealand: Kane Williamson (capt), Hamish Bennett, Trent Boult, Mark Chapman, Devon Conway, Martin Guptill, Kyle Jamieson, Jimmy Neesham, Glenn Phillips, Mitchell Santner, Tim Seifert, Ish Sodhi, Tim Southee.