This will have a domino effect, with Roberto Alagna replacing Kaufmann in Manon Lescaut....and Marco Berti replacing Alagna in Alagna's scheduled Pagliacci performances. It's best explained by the Met's press release:
Star tenor Roberto Alagna—currently at the Met giving an acclaimed performance of Canio in Pagliacci—will sing his first-ever performances of des Grieux in Manon Lescaut, replacing Kaufmann. To allow time for him learn the staging before theFebruary 12 new production premiere, Alagna must withdraw from his remaining performances as Canio as he undertakes this new challenge. The French tenor, who has sung more than 100 Met performances since 1996, learned the role of des Grieux for a 2006 series of performances that were canceled, meaning that this season’s Met performances are the first time he will ever sing the part onstage.
Marco Berti, currently starring at the Met as Calàf in Puccini’s Turandot, will replace Alagna as Canio in the remaining performances of Pagliacci. These performances will be Berti’s Met role debut as Canio.(Let's just say that at this point, I will faint if Kaufmann ever sings opera on the West Coast.)