Scrum-half Whitaker sustained a suspected broken ankle in the first period and he and his two team-mates were all expected to be treated in hospital.
Head coach Michael Cheika, who blamed "silly errors" for his side's second-half collapse after the game was tied 6-6 at half-time, said: "They all look like they're hospital bound at the moment so we'll have to wait and see and re-assess our situation from there."
Leinster captain Brian O'Driscoll pulled no punches in his assesment of his side, saying: "I think it was probably a fake first half and we probably didn't deserve to be level at 6-6. It was a very frustrating night and our backs let down our pack this week.
"We made some bad decisions, spilled a lot of ball and really shot ourselves in the foot.
"We'll have to have a good hard look at ourselves."