Barrett was sent off for a dangerous tackle near the end of the first half of the All Blacks 47-26 loss to the Wallabies in the opening Bledisloe Cup clash in Perth.
He'll likely be ruled him out this weekend's Bledisloe Cup decider in Auckland, but he could be slapped with a four week ban, which would rule him out of this week's second Bledisloe test in Auckland, the All Blacks one-off test against Tonga and their first two World Cup pool games.
The SANZAAR foul play committee adjourned last night's hearing pending further evidence.
Barret was red carded by French referee Jerome Garces for an apparent shoulder charge which struck Wallabies skipper Michael Hooper in the back and neck as the All Blacks were desperately defending their line.
All Blacks coach Steve Hansen indicated after the match there was some hope champion lock Brodie Retallick may be able to return at Eden Park on Saturday after missing the Bledisloe opener with a dislocated shoulder suffered two weeks ago against South Africa.
However it seems likely they may turn to 24-Test lock Patrick Tuipolotu to partner veteran Sam Whitelock in their second row as they attempt to retain the Bledisloe Cup, which they have held since 2003.
The bigger concern is Barrett could miss the start of the World Cup.
The offence usually carries a six-week ban and could put him in doubt for New Zealand's World Cup opener against South Africa in Yokohama on 21 September, another big blow after Retallick's injury.
All Blacks coach Steve Hansen said the red card had been costly even if he was more concerned about how many tackles his side had missed.
"It's not good enough when first half you miss 10 or 20 tackles out of 90 so we were not going well," he said.
"We were starting to get into the game and then, lack of discipline, we get a guy sent off and it's not a team you want to play with 14 against."
Hansen said he had been encouraged by the spirit shown by his team despite playing with one man fewer for half of the match.
"At the end of the day, both sides were out on their feet, so all credit to Australia, good win," he added. "Having said that, I'm still proud of our boys, the way they stayed in there with 14 men, they didn't lie down."
With Hansen on the record as saying the Bledisloe Cup is the second most important trophy for the All Blacks after the World Cup, the Wallabies could face quite a backlash at Eden Park next week.
"Lots can change in seven days," Hansen said. "Attitudes change, we probably won't have Scotty Barrett so we'll have to make some team changes, but we've just got to get our game going and play with a bit more confidence."
Barrett is only the fourth New Zealand international to be sent off during a Test match.
Cyril Brownlie in 1924, Colin Meads in 1967 and Sonny Bill Williams two years ago were the other All Blacks dismissed in tests. Garces also showed Williams his red card for a shoulder charge during the second British and Irish Lions test.