"I ask myself the same question all the time," Guptill told Radio Sport's Martin Devlin. "Just why? Why isn't it working?
"But I enjoy coming back to play for Auckland, and hopefully I can score a couple more hundreds before the season's end and put some pressure on the get back into the test team."
He admits he has discussed a change to his usual role with coach Mike Hesson, hoping that may provide a way into five-day consideration.
"I'd like to bat anywhere in the order. I've had a few conversations with 'Hess' about where I want to bat, and we'll have a little play around when the Plunket Shield starts up again and see what happens there."
With Tom Latham and Jeet Raval solidifying their opening spots, Guptill has his eye on the number five position currently occupied by Cantabrian Henry Nicholls, who made 98 in his last test outing.
"Obviously Henry played some useful knocks against Bangladesh and put a bit of pressure on to keep that number five spot.
"It's going to be hard, but at the end of the day, if you just keep scoring runs, you're asking the right questions. That's all I'm concentrating on at the moment."
His latest showing for the Aces showed he can approach the Australian series with some confidence.
"I was just trying to get a bit of time in the middle," he told Devlin. "It was a bit scratchy to start, but once you spend time out there and start to get some rhythm back, you start hitting the ball a bit better."
Despite the Black Caps' capitulation, Guptill starred with the bat in the pre-Christmas ODI series against the Tasman, scoring 114 off 102 balls in Sydney and averaging 64.3 across the three matches.
"It was pretty fluent that day [in Sydney]," he said. "I'd love to be able to do that every time I go out to bat, but I know that's not realistic.
"If I can do that a couple more times this summer, then hopefully I can win some games for New Zealand."