The Waratahs have suffered a double blow ahead of their Super Rugby clash with the Cheetahs after back-row Jed Holloway and hooker Tatafu Polota-Nau sustained shoulder injuries.
Holloway, who has been in impressive form this season at number eight, was injured in training after going to ground awkwardly.
According to rugby.com.au, his place in the starting side is likely to be taken by Wycliff Palu, with Ned Hanigan coming onto the bench.
His training ground injury followed Polota-Nau also being hurt as the Waratahs' preparations for Saturday's game require late changes.
The Waratahs are currently third in the Australian Group, level on points with the Brumbies and two behind the Rebels with a game in hand.