Perth Glory would be sitting pretty at the top of the A-League table if it wasn't for a series of silly mistakes that have cost them dearly this season, according to striker Mile Sterjovski.

The Glory slid to fifth on the ladder following last week's 2-1 loss to Melbourne, where again they were made to pay for slack marking in defence.

Sterjovski said the team's lack of awareness had become a concern but believed they could right past wrongs in Sunday's clash with Wellington at Westpac Stadium.

"The most important thing is to try to get consistency and cut out silly mistakes in our games," Sterjovski said.

"If you have a look at the goals we conceded, nine or 10 of those goals have been through little errors.

"If we didn't concede those goals I'm sure we would have had an extra nine points, which would have taken us to the top of the table."

Perth, on a three-game losing streak, are underdogs against the Phoenix, who have gone undefeated in their past 12 matches in Wellington.

Phoenix's past two games there have been particularly brutal, smashing Gold Coast 6-0 before dismissing Newcastle 3-0.

"It's one of the hardest places to play," Perth coach Dave Mitchell said.

"I was chatting with (Mariners coach) Lawrie McKinna the other day and he said people don't realise how tough that trip is.

"They're playing really well and I've always said Ricki (Phoenix coach Ricki Herbert) has done a good job.

"He's got them firing, they've got two quality strikers.

"They're a real threat and I think they'll make the finals."

Mitchell dismissed any notion the Phoenix could be vulnerable in what will be their third game in just seven days.

But the Glory coach conceded his defence would have to be on high alert to shut down Wellington dangerman Paul Ifill, who has scored four goals this season and set up plenty more.

"I knew he'd (Ifill) get better and better and I think Chris Greenacre is a great foil for him."

Perth's quest for victory received a blow on Friday when defender Jamie Coyne (thigh) was ruled out through injury, with youngster Scott Neville set to fill the void at right back.

But in a boost for Perth, striker Branko Jelic is set to return to the starting XI after missing last week's loss to Melbourne with a stomach bug.

Herbert is hopeful Phoenix goalkeeper Mark Paston will be fit after his recent hip problems.