Barenboim was elated with the evening -- citing the orchestra "capable of playing like hardly anyone in the world," the "stupendous" chorus and "top-notch" singers.
He acknowledged that a double illness was not normal even in the dramatic world of opera, but said he knew Dasch could step in having worked with her previously -- though never on Wagner. He said he has seen her voice develop from Mozart when she was young to more mature Wagner roles.
"Dasch, according to me, will be a great Wagnerian singer," Barenboim said.
The audience was completely won over from the first act, applauding enthusiastically at both breaks and giving no credence to media criticism that La Scala was inaugurating its dual bicentennial celebrations of its own Giuseppe Verdi and German icon Wagner with a Teutonic classic.
"Wagner always wins when you play the music well," Barenboim said.
Premier Mario Monti, a La Scala regular, took a break from the grueling job of reforming Italy's economy and after Thursday's moves by Silvio Berlusconi's center-right party to pull support from the government. He went back stage to meet the singers during one of the intermissions.
With no time to rest on her laurels, Dasch heads back to Berlin early Saturday for an evening performance of Mozart's "La finta giardiniera" (The Gates of Love).
"Something completely different," she said.