Man-of-the-match Mccullum slammed his maiden World Cup century (101 off 109 balls) as New Zealand routed minnows Canada by 97 runs after amassing 358 for six in their penultimate Group A match at the Wankhede Stadium here today to seal a berth in the last eight stage.
After today`s victory, New Zealand are on top of Group A with eight points from five matches and they play their last league match against Sri Lanka at this venue on March 18.
"It is work in progress, the tournament is going on for 7-8 weeks, quite a long tournament. We have to build up some momentum before the knock-out stage," McCullum said.
New Zealand had approached the tournament with some trepidation after having been outclassed by Bangladesh and India in sub-continent conditions and by Pakistan at home just before launching their Cup campaign.
"When we came here (to the World Cup) we were going through a very tough time. After (coach) John (Wright) came (on board), each of us got a specific role and we know what is expected of us," he said.
The stumper batsman was pleased that the top order of his team`s batting line-up had performed well in the tournament barring the defeat to three-time defending champions Australia at Nagpur.
"I think so far the top order in the tournament has done well barring one game. Some of the guys had not spent time in the middle. They set up the last ten overs (when New Zealand added 122 runs). That gives us confidence (in future assignments in the tournament)," he said.
McCullum also said that the 110-run victory over Pakistan in their last league outing was a very crucial one for the team`s Cup campaign.
"The win (over Pakistan) was a key victory for us in the business end of the tournament. Today`s victory was also important," he said.
Apart from his match-winning knock, the Black Caps stumper also snapped up three catches and contributed to a rival batsman`s run-out dismissal.
"Was a busy day today, one of those days when you walk off your mind is fully tested and thankfully I came out no 1 today. Today was my opportunity. It was only my third century in my ODI career. Will take that one and try to get many others."
McCullum was also full of praise for the manner in which the newly-laid pitch at the refurbished stadium, which hosted its first international match after three and a half years, behaved right through the tie.
"In the first 8-10 overs it (ball) went over a little bit. Then it (pitch) got better and better for batting. (There was) enough pace and bounce. It was a very good wicket. The stadium was fantastic," he said.
On the injury to speedster Kyle Mills, who limped off after taking two wickets in 16 balls that reduced Canada to 4 for 2, team`s media manager Ellery Tappin said it would need 48 hours before anything more can be said.
"It was a s train in the quadriceps of his left leg. He will be kept under 48 hour observation," he said.
McCullum did not read too much into the injuries that have laid low Mills and captain Daniel Vettori, who has strained the ligament of his right knee and missed today`s encounter.
"Injuries are part and parcel of the game. Every team has gone through it. Got some fine players we look at this as an opportunity to find out what we are missing," he said.