Popovic is a clear admirer of Yengi, who was released by club side Portsmouth earlier this month after failing to score across 14 games in the English Championship in an injury-ravaged campaign.
The 26-year-old is on the hunt for a new club as he fights to be a part of Australia's squad for next month's qualifiers against Japan and Saudi Arabia where two wins would rubberstamp the Socceroos' passage to next year's World Cup.
Yengi, an 11-cap international, is currently in camp in Abu Dhabi alongside former Western Sydney Wanderers teammate Borrello with Popovic due to name his squad for the June 5 clash with the Japanese in Perth and the away trip to Jeddah on June 11.
"Kusini is one of the most professional athletes I've seen. He's got the body, the tools … he's an absolute monster," Borrello said.
"It's just (about) making sure he stays fit and on task.
"We've seen previously what Kusini can do and he is a joy to watch on the pitch.
"I guess getting into the rhythm of training, finding your feet, and then hopefully playing games and I think he'll let the rest do the talking."
Yengi and Borrello are competing with Perth's Adam Taggart and Mitchell Duke, who is not in the UAE due to club commitments in Japan, to lead the line next month.
Borrello said Popovic's training intensity meant the Abu Dhabi trip was by "no means a holiday".
But 13-cap striker Borrello claimed the extended period of fine-tuning the coach's tactics ahead of the Japan and Saudi fixtures had the Socceroos primed to deliver and book their spot at the World Cup.
Australia beat China 2-0 on the road and thrashed Indonesia 5-1 in Sydney in the March international window.
"Building from China and Indonesia, which was also a great game in terms of the amount of goals against, it (shows) a progression," Borrello said.
"From the back, it's filtering in through to the midfield (and) to the front third.
"When that all becomes fluid, who knows what's going to happen and what our limits are? Because we are, I would say, underestimated as a country, attacking wise."
Popovic will name his squad for June's qualifiers following Saturday's A-League Men grand final between Melbourne City and Melbourne Victory.
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