New Zealand thumped Pakistan by an innings and 80 runs to level the three-match series 1-1 in a match overshadowed by Australian batsman Hughes's untimely death on Thursday.
"It certainly wasn't easy," said McCullum. "It was a very tough period. We are nowhere as affected as the guys back in Australia, but at the same time, cricket is a community ... It is a fraternity and we felt we lost one of our own."
McCullum said the tradegy hit players hard.
"It hit the guys pretty hard and we tried to stay as close as we could as a group. We tried to spend a lot of time together and tried to talk through stuff and share one another's thoughts.
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"It felt incredibly hard to focus on the game and still hard to talk about the game. We will look back upon this performance in time and we will be really proud of what we have been able to achieve," said McCullum who hit a robust 202 which helped his team post their highest-ever Test total of 690.
McCullum praised his team's fightback after losing a crucial toss and Pakistan racing to 281-3 on the first day.
"I am proud of the way the boys bounced back under trying circumstances. We stuck together on and off the field. But to bounce back the way we did by taking those seven wickets in the first session on the second day and then take the momentum into our batting and score at five an over, we were just playing with no inhibitions whatsoever.