New Zealand captain Brendon McCullum has backed England counterpart Eoin Morgan to emerge from his alarming slump in form and return as a better player.

The 28-year-old has taken just two runs from his last five innings ahead of tomorrow's Wellington meeting between the two sides at the Cricket World Cup.

However, McCullum believes that his close friend will reap the rewards of his current barren run when he eventually returns to his best.

"I caught up with Morgs last night," he is quoted as saying by ESPN. "He's a champion player, probably one of my better mates from around the world in terms of cricket. He's obviously going through a bit of a tough time at the moment.

"Hopefully at some point he'll come out of it. Hopefully tomorrow we're able to keep him quiet, but he's a quality player and he's a tough bloke too. The hardest time, and the most important time, to lead from a captain's point of view is when you're probably struggling a little bit with your own form.

"That's when guys are looking to you to see whether you still have it in you to think about the team and the team's gameplan, and to drive the team ethos forward. It's the hardest time, but it's also the most rewarding when you do come out through the other side of it. I'm sure Morgs, knowing him, he will be very much focusing on the team, albeit wanting to get his own performance up."

Victory for New Zealand over England will see them all but secure a place in the quarter-final stage of the competition.