Flower, back with his England charges for the first time since their historic series win in India last year and in his new guise as their specialist Test coach, watched them lose their only warm-up fixture before a three-match series which starts in Dunedin on Wednesday.
The three-wicket defeat was a setback as England sought to create winning momentum before getting down to more serious business.
Moderate first-innings bowling and inconsistency among their top six batsmen cost them at the Queenstown Event Centre ground, where a New Zealand XI chased 334 to win with eight balls to spare on Saturday. "We went into that four-day game wanting to win it," said Flower.
"Winning is a great habit to keep. But they played pretty well, and I thought we were a little sloppy in a few areas."
Flower was encouraged by a gradual improvement from the bowling attack, minus the rested Steven Finn and James Anderson, and the batting of first-innings centurion Ian Bell and Matt Prior.
"There were some good things to come out of that game," he said.
"I thought Bell and Prior were excellent with the bat. The bowlers, after a poor first-innings display, all got better in the second innings."
He therefore believes there will be more significant improvement from England this week, saying: "It's not ideal losing.
"But the crux of the matter is the first Test is four days away, and that's when it will count. I think there was ring-rustiness there, without a doubt. That was obvious for all to see. The point of playing these games is to get ready for the first Test.
"It was an excellent game of cricket ... all in all, a very good outing for everyone."