New Zealand will leave a decision on whether they will field their left-arm spin bowler Daniel Vettori in the second National Bank Series Test against England, until the last moment on Thursday.

Vettori is under constant surveillance by medical officers with the New Zealand side and he is being assessed after each bowling stint at practice.

He had been quite good after bowling on Monday and it had been encouraging to see him get through a lengthy session today at the Basin Reserve, New Zealand Cricket's sport science medical co-ordinator Warren Frost said today.

"We've got till 10 o'clock on Thursday morning to make the call so we want to give him as much time as possible so we are aware of the long-term impact as well," he said.

Frost said that the medical panel policy was that if they pass a player as fit there are no limits on what he can or can't bowl.

What the medical advisors did was assess the risk and pass the information on to the selectors and it was the selectors who then weighed things up and made the final choice.

"We think it is mainly disc-related so it is a soft tissue-type injury which is different to the stress fracture that he had about two years ago," he said.

"You will find that Dan will have periods of back pain throughout his career which is not uncommon for bowlers and it wouldn't be correct to say that he is never going to experience back pain again," he said.

Frost said fast-medium bowler Chris Martin, who had a back problem in Christchurch, had been feeling much better today.

England will choose their side for the Test from all the available fit players - and that includes Ian Bell once he arrives.

While there was still some concern over batsman Mark Butcher, who injured a finger when catching Lou Vincent out in the second innings of the first Test in Christchurch, a final decision will not be made on his availability until after a net session tomorrow.

England captain Nasser Hussain said when Bell arrived he would be in the squad and available for selection, just like every other fit player.

Butcher had a net today and was still feeling some pain but he would be given another chance tomorrow to see if there was any improvement.

Hussain said his own hand was fine batting but still a little tender when catching and just how that recovered would determine whether he will be at first slip when the Test starts on Thursday.

"Batting is the most important thing and that felt 100%.

"It was a jarring injury and everytime the ball doesn't carry it is in my mind a little. It is a psychological thing," he said.

Hussain said it had been a long winter for everyone, both England and New Zealand, and there were a lot of niggles around for both teams.

© CricInfo