Pencilling in David Warner and Steve Smith into the top-order could be a headache, but there is no doubt the pair would only make the playing XI richer as they strive to defend their World Cup crown, feels former batsman Simon Katich.

While Warner has been in the form of his life, finishing the IPL as the highest scorer for Sunrisers Hyderabad, Smith stamped his class in the warm-up games against New Zealand.

"They are both quality players and their records speak for themselves. The hard part is the Australian team has a problem of plenty particularly in the top four.

"Both of them are top four players. There is (Usman) Khawaja, (Aaron) Finch, Shaun Marsh, and the two and these guys will try to fit into four slots. Then there is Maxwell, Stoinis. It's going to be a tough selection call," Katich said.

For the defending champions, the primary selection question centres on how to fit in Aaron Finch, Usman Khawaja and Warner into the top three.

After the World Cup, Australia will take on England in the Ashes.

"They will welcome back the experience of Smith and Warner," said Katich when asked about the off-field baggage that comes along with the pair.

"The balance with the batting line-up is what they need to get right," the 43-year old reiterated.

Katich, who worked closely with India's World Cup bound wicketkeeper batsman Dinesh Karthik during his time as assistant coach of the Kolkata Knight Riders, also threw his weight behind the 33-year old whose selection raised a few eyebrows.

"There is a lot of talk around that No 4 spot, and he is a guy who likes to spend time in the middle. Once he is set, he is very hard to bowl to at the back end. He has got all the tricks and he does have the timing and power to clear the rope," said Katich who has played 56 Tests and 45 ODis for Australia.

"It's hard to judge a player based on T20 cricket with ODI cricket," he concluded.