From a press release on August 20, 2012.
Janai Brugger makes her Met debut as Liù in Turandot on October 30 and sings the role on November 2, 5, and 9. Brugger replaces Takesha Meshé Kizart, who is recovering from recent abdominal surgery.
Guanqun Yu replaces Sondra Radvanovsky as Leonora in Il Trovatore on October 17, 20, and 25. This role marks her Met debut as well.