An army of Fijian fans almost willed the visitors to a stirring victory at Allianz Stadium before the Waratahs escaped with a late penalty try on Friday night.
Referee Angus Mabey gifted the Tahs the winning points and yellow-carded Drua loose forward Kitione Salawa for crudely stopping a NSW driving maul three minutes before fulltime.
It was the second straight Houdini act for last year's wooden spooners after they also denied the Highlanders in round one with a last-gasp try to Siosifa Amone.
"Speaking to the boys, I think they all agree that they probably would have lost that game in the past," McKellar said.
"So it's pleasing that we sit here again after grinding out and fighting our way to win knowing that we've got enormous improvement in front of us."
In stark contrast, the deflating defeat for the Drua was their third heartbreaker in a row, after they also blew leads late on against the Brumbies and Hurricanes.
And it was NSW's Fiji-raised back-rower Langi Gleeson who stole the show this time around.
In a powerhouse display, Gleeson collected his first try-scoring double for the Waratahs while also featuring in two huge defensive saves in the second half.
Twice Gleeson helped hold up Drua ball carriers over the line during the frenetic finish.
"(This) means everything. It's special to play against the Fijian brothers," Gleeson told Stan Sport.
"It's always tough on the field but afterwards we can have a laugh.
"A special shout-out to the boys that came off the bench. They worked really hard for us. And Drua, it's always hard to play them whether it's their turf or ours."Intent on not being drawn into the Drua's razzle dazzle style of play, the Waratahs started the brighter of the teams.
But it was a loose ball that broke the early deadlock when Meli Derenalagi pounced and laid it off to winger Ponipate Loganimasi, who steamed down the left flank for the opening try.
The Waratahs bounced back to level up immediately when Gleeson crashed over off a short ball from Jake Gordon.
And the frenzy continued when the Drua opened up the NSW defence before Vuate Karawalevu dived over in the right corner.
The Waratahs began to strengthen their grip on the game, but it didn't show on the scoreboard as errors halted opportunities for points.
But they finally found a way through to snatch a 17-12 halftime lead after a seemingly innocuous kick from Gordon led to Gleeson's second try.
Drua flyhalf Caleb Muntz cleaned up the kick close to his own line, only to lose the ball in a tackle from Max Jorgensen before Gleeson swooped.
The Waratahs looked set to rack up a comfortable win when hooker Dave Porecki finished off a signature rolling maul try three minutes into the second half to extend the lead to 10 points.
But, inspired by their feverish fans, the Drua lifted and began to sap the Tahs of energy with their free-wheeling attack.
The Waratahs defended their line desperately for what seemed an age but couldn't hold out any longer while lock Miles Amatosero was in the sin bin for a professional foul.
Loganimasi bagged his second try of the night, and replacement hooker Mesulame Dolokoto also crossed soon after to briefly restore the Drua's lead.
But the penalty try cruelled the Fijians, who remain winless after three rounds.
