Australia's captain believes it's still "mathematically possible" for his team to make the quarter-finals following their dispiriting 3-0 loss to Croatia in Thursday's opening group in Turin.

Yet Hewitt also knows, with Australia now unlikely to qualify as group D winners, they'll have to beat Hungary 3-0 on Saturday night and hope results in the other five groups conspire to allow them to make the last eight as one of the two best runners-up.

They can't afford another slip-up and Hewitt has decided against risking Alexei Popyrin, who cut a forlorn figure after losing tamely to Croatian long-shot Borna Gojo on Thursday.

It was only Popyrin's second Davis Cup appearance and he was found wanting against a player ranked some 215 places behind him on the ATP computer.

Popyrin admitted afterwards he felt it was "probably the most painful loss" of his career and Hewitt has opted to play the 72nd-ranked Millman against Hungary's world No.282 Zsombor Piros in Saturday's opening rubber.

Australian No.1 Alex de Minaur, currently ranked 34th, will play world No.40 Marton Fucsovics in the second singles match.

Hewitt has named Alex Bolt to partner John Peers in the doubles, after using de Minaur against Croatia.

Hewitt promised his side would "leave absolutely everything on the court in those three matches" against Hungary.

"The boys will certainly be going out there and doing absolutely everything in their power to get the result we want," the skipper said.

But even that may not prove enough for the 28-time champions, who are seeking to lift the Cup for the first time since Hewitt, as a player, won the trophy for the second time in 2003.

Australian Associated Press