SYDNEY — United States Olympic rugby star Alev Kelter will face a judicial hearing and potentially lengthy suspension after being sent off in a women’s rugby test against Australia on Saturday for stamping on the head of an opponent. Kelter received a straight red card in the 79th minute of the Pacific Four Series test against Australia after referee Aimee Barrett-Theron reviewed footage that showed Kelter stamping forcefully on the head of Australian center Georgie Friedrichs. In comments captured by television microphones, Barrett-Theron said “12 blue (Kelter) is going to receive a permanent red card because this is thuggery, it is deliberate and it is very dangerous foul play. “She’s clearly stamped on the head of the Australian player. That’s reckless, that’s dangerous and she’s going off.” Friedrichs was not seriously injured in the incident. The United States team coach Sione Fukofuka later apologized to the Australian players. Foul play in rugby that involves contact with the head is treated with extreme seriousness. Rugby, like many contact sports, has changed its rules in an effort to limit the danger of concussion and other head injuries. Kelter is a three-time US Olympic representative in rugby sevens and won a bronze medal in Paris last year. She previously played ice hockey and soccer for the University of Wisconsin. In rugby, judicial hearings over foul play usually take place withing 48 hours of a match. Australia won Saturday’s match 27-19.