It strikes me as being a bizarre way to handle casting, but here goes.
You get a not-very-good tenor - Salvatore Licitra - pulling out of Il Trovatore, no doubt to huge sighs of relief all round, especially when it is announced that the replacement is an excellent tenor, Marcelo Alvarez. Not one to question a star's choice of parts but it seems a no-brainer to me: Il Trovatore is a nearly great opera with title role for tenor. And a cross-section of 57 Old Farts on a certain Opera List say they can't imagine Marcelo as Manrico (he's not performed it in their world ergo he hasn't performed it...). Bloody good, he is
So, getting an excellent tenor to cover for a not-very-good one, means that you have to find someone to plug the gap for the now vacated part of, erm... quickly searches Wikipedia (and spells the opera wrong)...Maurizio in Adriana Lecouvrer. You only have two choices - either you get the conductor to sing it, or else you get a legendary tenor to sing it. Or both. Domingo to Reprise the Role of His Met Debut! Tempting though it may be to book a birthday trip to NY for my birthday, I think I'll pass. I don't know the opera. I might have heard it once or twice, it doesn't interest me (except that, of course I'll endure a few times at Covent Garden in 09/10 with Morticia and Jonas...hmm, I wonder who'll be covering for Jonas in that production - vg, as they say on some newsgroups.
Meanwhile, a similar but different cross-section of the 57 Old Farts have already declared it an artistic disaster*. I must admit I really didn't see that one coming even though there has been some speculation about who would be the replacement. I did think that the original posting was one of those spoofs that people with time on their hands post from time-to-time, especially as it hadn't come up in a Google Alert. Seeing that it's on the Metropolitan Opera website, I suppose it must be true. I don't know when Plácido last sung the role, but he first sung it in 1962 in Mexico City.
* although in fairness, a dissenting voice has weighed in with:
how many times have we been warned that this or that will be a mistake for him, yet he always proves the doomsayers wrong. Conclusion: he has better judgment than anyone else regarding what he can or cannot do.