A double to prolific striker Kate Gill, including a controversial penalty, and a first-half goal from Shelina Zadorsky were enough to hand United (3-2) its second defeat of the campaign.

United had won seven and drawn three of its previous games with the Glory since the inception of the W-League in 2008.

However, the Glory is enjoying its most successful start and is the only team to maintain a 100 per cent winning record through the opening five rounds of the competition.

United captain Nicole Begg lamented her side's inability to finish off its chances in front of goal while the defence failed to deal with the Glory's set piece.

"We wanted to continue that good streak and we thought we could as well," Begg said.

"It's disappointing that we weren't as clinical as we needed to be in and around the box, both defending and attacking, that's what let us down.

"Overall it was a pretty hard-fought match, but they really capitalised on their chances."

With United down 1-0 at half-time, United goalkeeper Chantel Jones gave away a penalty and was handed a yellow card for colliding with Glory striker Sam Kerr in the box.

United assistant coach Raeanne Dower was left perplexed at the decision.

"Chantel's come out, won it cleanly in a blocked tackle and there's been a collision afterwards and it's been claimed there's a reckless challenge," Dower said.

"There already seemed to be some push me, shove you a little bit earlier, so I think the resulting penalty was a little bit harsh in the circumstances.

"We came straight back out and created a couple of chances, but unfortunately today their goalkeeper (former United 'keeper Mackenzie Arnold) had quite a good game.

"She probably wanted to play well against her old team as well.

"Mackenzie saved three or four one on ones and that probably proved the difference."

All three goals that United conceded were off set pieces.

The first was a corner in the 14th minute, when Zadorsky was in the right place at the right time to open the scoring.

Gill converted from the penalty spot early in the second half before sealing all three points off a corner 10 minutes from time.

"We just need to back ourselves," Begg said.

"We've got the talent, we've got the skills, we've just got to make them match up.

"It's not quite clicking for us, I don't think, across the park and we've got to be a bit more clinical with the basics that we do."

W-LEAGUE: Perth Glory 3 (Shelina Zadorsky 14', Kate Gill 63' (pen) 80') bt Canberra United 0 at Ashfield Sports Club, Perth, on Saturday.