"I think it's a ruthlessness - being really determined to score a goal," he said. "We just seemed to be lacking that, going in with absolutely everything you've got.
"It's the old cliche, when the boots are flying and it's dangerous, having that real killer instinct and we just didn't seem to have that tonight.
"It's something that's born within you."
- AAP
Smeltz scored 21 goals for the Phoenix in two seasons, before transferring to the now-defunct Gold Coast United in 2009, his career going on to include stints at Perth and Sydney FC.
It's the sort of pedigree that has Greenacre confident the 35-year-old striker will be a valuable acquisition.
"It's natural - you can't coach it, that instinct to be where the ball is," he said. "Shane's certainly got that.
"I've no doubts he would have probably scored tonight."
Smeltz is expected to make his impact from the bench against Perth on Thursday, although Greenacre and Buckingham have yet to finalise their squad.
They'll be missing defensive midfielder Vince Lia, as he serves out a one-match suspension for his fifth yellow card of the season.
And All Whites playmaker Michael McGlinchey is in doubt, after his planned return from a knee injury was put back a few days, when he tweaked a calf at training.
In tandem with Alex Rodriguez, also working his way back from injury, McGlinchey offers a range of mid-field options for Greenacre and Buckingham.
The duo say the focus this week will be on keeping possession, particularly in the attacking third.
"The back-line and mid-field, especially, kept the ball really well," Buckingham said.
"But when we got into the front third, it seemed rushed or there was a laziness to the pass, and we just couldn't get into the areas we wanted.
"That'll be the focus for this week."
