The 24-year-old injured his thigh during pre-season training, and Waratahs coach Ewen McKenzie said he is unlikely to risk the versatile back against the Hurricanes on Saturday night.
"Sam's taking a little longer to get back to 100% but we don't want to rush him," McKenzie said.
However, McKenzie is confident that Lote Tuqiri will be fit in time for the Hurricanes clash, after the Wallabies star underwent surgery last month.
"The good news is that Lote is pretty pumped up and ready to go so we'll see on Tuesday," McKenzie said.
The Waratahs finished their final pre-season run-out with a come-from-behind 24-14 win over the Crusaders in atrocious conditions at the Sydney Football Stadium on Thursday night.
Waratahs pivot Kurtley Beale was particularly impressive against the Crusaders, and half-back Brett Sheehan displayed his poise with an excellent performance in trying conditions.
And McKenzie believes his team is heading into the season opener in fine form.
"We've had a good look at our trials and taken some injuries into account so we should be in position to name a strong side for the Canes," McKenzie said.
"Like us the Canes are coming off a big win over the Brumbies. We both scored a lot of second-half tries so this first-up clash should be an entertaining one."