''It appears to have deteriorated a little bit. Ross had his (regular check) six months ago and there were no issues at all. So it might have come a little quicker than we'd like," Hesson added.
Captain Kane Williamson, who is the only current player with a better test average than Taylor's 45.95 from 77 tests, said he understood it had been a gradual change rather than sudden in terms of Taylor's vision.
''There's a growth that's come across a little bit. It's been fine for a long time but it's part and parcel for any human being. You do different tests, you want to make sure things are all in order."
Taylor, 32, has been in a form slump for some time, with just 103 runs in his last 10 test innings. He's scored 15 test hundreds, more than any New Zealand batsman, other than his mentor Martin Crowe's 17.