After only returning three weeks ago from a hamstring tear, Suaalii was a late scratching from last Saturday's season-saving 50-35 victory over the Fijian Drua in Suva.
Coach Dan McKellar on Wednesday said while Suaalii's latest setback wasn't serious, it was too "high-risk" to rush the code-hopping game-breaker back to face the Brumbies in Sydney on Friday night.
"He was a possibility. If it's a grand final, you'll probably roll him out," McKellar said.
"The travel has probably taken its toll. When he's sitting in economy class for a fair amount of time, a long travel day off the back of playing in Dunedin as well, that's probably played a role in where he's at.
"But he ran this morning and we're hopeful that he'll turn around quickly. Certainly there's been no re-tear or incident, it's just not quite right. If he's a tighthead prop, you can probably get away with it, but when you're the athlete that he is, it, it would be high risk."
Star halfback Jake Gordon was rested for the Fiji trip but remains sidelined this week through illness.
McKellar was happy to continue backing Teddy Wilson at No.9 after naming an unchanged starting line-up.
"There's a whole lot of energy off the back of the performance and the momentum that we created from that (weekend win), and we probably built a little bit of momentum that last half-hour against the Highlanders," the coach said.
"As disappointing as that first half was, the second half was better, so the players that did the job in Suva have presented up fresh and excited to rip into what's a step up against the Brumbies."
Sitting three points behind the fifth-placed Brumbies in seventh spot, the Waratahs likely need to win on Friday and then beat the Western Force in Perth in the last regular match of the season to make the top-six finals.
"I don't really need to talk about it," McKellar said.
"Everyone in the building knows that this is a big game and an important week, and we've spoken in the past about ... some games are just different.
"Brumbies versus the Waratahs, it's one of those weeks on any given week.
"But certainly when we're both chasing the same prize, it adds to that."
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