Pulu, who joined the Canberra-based side this season with an eye on forcing his way into Michael Cheika's Wallabies squad, lasted less than 10 minutes with his new club against the Melbourne Rebels before he suffered the injury on Friday.
The 30-year-old, who was born in the United States and played rugby sevens for Niue, can represent Australia through his parents.
Once dubbed the fastest man in New Zealand rugby, Pulu was invited to a pre-season camp by Cheika as he assessed players he was interested in ahead of this year's showpiece in Japan.
