Write off David Warner at your peril. That is the warning from Australia teammate Glenn Maxwell following Warner's first-ball duck in the World Cup warm-up game against New Zealand on Monday night.

Warner's form has been a cause for concern for Australia heading into this World Cup with the veteran dropped by Sunrisers Hyderabad for the second time this year during the second leg of the IPL, after scores of 0 and 2 when the tournament resumed in the UAE in September.

He did not play the remainder of the IPL before heading into the Australia camp ahead of the World Cup. But his lean run continued on Monday night in the first warm-up game against New Zealand, when he fell for a first-ball duck after advancing at Tim Southee and edging him to slip where Martin Guptill held a spectacular one-handed catch diving full stretch to his left.

Maxwell warned against anyone writing off Warner ahead of the World Cup, backing his long-time teammate to return to his best when Australia's tournament begins on Saturday.

"If you ever doubt Davey, it's an absolute no-no," Maxwell said. "You know he's going to turn it around. He's a superstar of all three formats. He's made so many runs. He's going to go down as one of the greats of the game. Unfortunately, he got Martin Guptill'd yesterday with an absolute hanger. Gup seems to do that a lot against us.

"Those sorts of things happen when you're searching for it. But you know when he gets out there come game time, come the 23rd [of October], regardless of what happens in the next practice game, you know he's going to hit the ground running. He's going to be a big player for us."

Maxwell was rested from the warm-up victory over New Zealand after an outstanding finish to the IPL. Many are predicting he will be the key man for Australia during the World Cup. But Maxwell is backing another allrounder in the Australia side to have a huge impact.

"I think Mitchell Marsh is going to have a massive tournament," Maxwell said. "I don't think I've seen anyone hit the ball better, ever.

"We all gather around his net and just watch him hit the ball. It's been pretty extraordinary to watch him go about his business at the moment. I'd be really surprised if he didn't have a really good tournament. He's got his bowling as well. His presence around the group regardless of what he's doing is second to none. He's the guy everyone wants in their team, he's flying at the moment, so I'm expecting him to have a good tournament."

Marsh batted at No.3 against New Zealand and looks set to stay there for the tournament. Steve Smith batted at No.4, although Maxwell looks set to play the same role he did for Royal Challengers Bangalore as first drop after the powerplay, which will likely see Smith float depending on how Australia structures their team. Maxwell was unsure whether he would play in Wednesday night's warm-up game against India, which will be Australia's last practice match ahead of their World Cup opener on Saturday against South Africa.