The Waratahs failed in their bid to have four and two-week bans against Tolu Latu and Will Skelton respectively quashed on appeal on Thursday.
After a four-hour hearing, SANZAR upheld the original penalties handed down to both players for their 17th minute tackle on Crusaders second rower Sam Whitelock in Sydney last weekend.
The decision leaves the defending champions without their damaging second rower for two of the team's three final, crucial regular season games, and means there will be extra pressure on Wallabies hooker Tatafu Polota-Nau to return early from a three-week rest period.
With Latu out for four weeks, third string hooker Hugh Roach will start against the Lions in Johannesburg this weekend, with Manly No.2 Dave Porecki as backup.
Polota-Nau was given a three-week break due to ongoing concussion concerns, but has been in Melbourne this week for further testing. There is a strong chance he will be cleared to join the team in Bloemfontein next week, when they face the Cheetahs.
Returning Waratah Dean Mumm has joined the squad in South Africa after finishing a three-season deal with Exeter Chiefs in the English Premiership.
He is likely to be named on the bench behind captain Dave Dennis and Mitchell Chapman.
The team are in Johannesburg preparing for their round 16 game against the Lions, and had postponed naming their team pending the appeal outcome.
The decision is a blow for the Waratahs, who argued that the tackle did not meet the red card threshold under section 10.4 (j) of the World Rugby laws, which states: "Lifting a player from the ground and dropping or driving that player into the ground whilst that player's feet are still off the ground such that the player's head and/or upper body come into contact with the ground first is dangerous play".
