Something positive looks likely to emerge from left-arm spinner Daniel Vettori's injury-forced absence from international cricket.

Vettori suffered a stress fracture to his back during the 1999/00 Test series with Australia and while coming back to start out on the tour of Zimbabwe later that year, he was forced out when the injury re-surfaced and was properly diagnosed after more intensive scans.

New Zealand Cricket's director of player development Ashley Ross said Vettori's absence and the prospect of his injuries being career-threatening had resulted in a much more serious attitude being taken to changes in Vettori's bowling style.

Problems with his style had been diagnosed before last year but Vettori had been reluctant to change because of the lack of time to make changes during New Zealand's intensive programme and they hadn't been pursued as slow bowlers were not perceived at much at risk as faster bowlers.

NZC utilised facilities at Auckland University which allowed three-dimensional camera studies to quantify angles and degrees in Vettori's bowling action. The work was aimed at improving Vettori's core stability.

"It didn't produce any revolutionary information but it did put numbers on what we've observed before," Ross said.

The main interest was in working on the hip and shoulder angles of Vettori's bowling.

"We have been making those changes. Daniel is a very talented athlete and he has incorporated the changes very quickly into his bowling," he said.

In practical terms, Ross said, the most obvious changes to Vettori's action would be seen in his running into the wicket a little straighter. His front leg will kick straight towards his target and his hips will also be straight on to his target and in line with his shoulders.

"He will have far more body in his posture.

"The spine is designed to take an impact, as long as it doesn't combine with rotation," Ross said.

Spin bowling was often referred to as a science from the ground to the elbow and an art from the elbow to the fingers, Ross said, and Vettori's control of the art aspect had been magnificent. The changes in style were aimed at lifting the science aspect to the same level.

© CricInfo