Fleming, 33, will overtake Sri Lankan Arjuna Ranatunga for a new One-day captaincy record as both teams seek a win to nudge ahead in the semi-final race from group B that remains too close to predict.
All four teams in the group - Sri Lanka, New Zealand, Pakistan and South Africa - are in contention for the two semi-final spots with three key games still to be played.
Sri Lanka and New Zealand have a 1-1 record from two matches, while Pakistan won the only match it has played so far. South Africa's lone game ended in a defeat.
New Zealand must beat Pakistan on Wednesday to stay in the hunt, irrespective of the result of Tuesday's match between Sri Lanka and South Africa in Ahmedabad.
"I would prefer not to worry about other teams and just concentrate on what we have to do," said Fleming. "And that is to win our last game against Pakistan."
The Black Caps upset world number two South Africa in their first match at the Brabourne stadium in Mumbai before losing to Sri Lanka by seven wickets at the same venue on Friday.
Pakistan overcame the absence of banned skipper Inzamam-ul-Haq and the drug-tainted pace duo of Shoaib Akhtar and Mohammad Asif to stun Sri Lanka by four wickets in Jaipur.
"The biggest worry for us is that we have been inconsistent in big tournaments," said Fleming, a veteran of 255 One-dayers. "I think we are a side that gets a bit comfortable once it has won a game."
New Zealand are hoping the cooler climate of northern Mohali and a wicket with more bounce than the one at the Brabourne stadium in Mumbai will come to the aid of injury-prone pace spearhead Shane Bond.
Bond, who missed the first match with a stiff back, was pounded for 47 runs in seven overs by the Sri Lankans on his return, made worse by five no-balls and two wides.
But for Bond to fire, New Zealand need enough runs on the board, something they have not been able to achieve in their first two games.
Totals of 195 against South Africa and 165 against the Sri Lankans meant the Black Caps fell for sub-200 scores batting first for the first time since May, 2003.
Middle-order batsman Hamish Marshall has failed to reach 20 on 16 of the past 20 appearances at the crease and must be in serious doubt against Pakistan.
Meanwhile, Pakistan's task will be to hit the groove again after sitting on the sidelines since their game against Sri Lanka last Tuesday.
"We have either watched others play or have been at the nets in this time," said stand-in captain Younis Khan. "We just can't wait to get back on the field."
Younis said his team was motivated to go the distance in the biennial tournament, regarded by the International Cricket Council as the second most important after the four-yearly World Cup.
"It was a good win against Sri Lanka which proved that we play our best cricket when things are not going in our favour," said Younis.
"But we can't afford to relax. Beating Sri Lanka will be of no use if we lose our remaining two matches. Each game is like a semi-final to get into the semi-finals."
Pakistan's last league match will be against South Africa here on Friday.