Vettori bowled 22 overs on the second day of the first test against Pakistan at Seddon Park here today, conceding just 29 runs in a typically miserly spell as Pakistan reached 235 for four in reply to New Zealand's first innings of 275.
But Vettori appeared lethargic, and New Zealand team manager Dave Currie tonight confirmed the captain had been suffering from an as-yet undiagnosed illness.
"Clearly he is not a million dollars, you can see that, but he's well enough that he's played," Currie said.
"The health team aren't sure what it is, he's had some tests, we'll have the results in a couple of days and we'll see what happens."
Currie said Vettori had flu and fever symptoms, but he was "battling on for the team".
"As you can see he's a bit listless in the field but he's carrying on. There's no great drama."
Former international Dion Nash said on a radio commentary today that one of the tests Vettori had was for malaria, but Currie said he had no knowledge of that.
"I don't know where he got that from. He's had blood tests for whatever, so where he made that speculation from I have no idea.
"He (Vettori) has been in India (on tour in November-December) so I guess you test for everything, but there's no speculation that's what it is at all.
"The reality is he's playing, he's not on death's door."
New Zealand seamer Brent Arnel described Vettori as a "very tough guy" and the fact he was playing in the test showed his "passion".
"Maybe a lot of other guys would be back in the hotel room sleeping it off. He's just such a courageous leader and its great to see him out there and fighting it," Arnel said.
"We know he's not too well and to see him bowling like that is magnificent. Again, he's unlucky because he could have had a couple wickets."
