Renée Fleming isn’t getting any worse, is she? Consider her recent performances at the Metropolitan Opera. Last season, she gave a near-perfect Tatiana (in Tchaikovsky’s “Eugene Onegin”). And on Saturday afternoon, she gave a near-perfect Violetta (Verdi’s “Traviata”). The American soprano is enlarging what will later be her legend.

You know what a great Fleming performance is: I don’t have to tell you much about it. She had supreme confidence, completely justified. The technique was secure; she could concentrate on the musical and dramatic. Her top notes were free and affecting; and, among sopranos, she has one of the great bottoms (pardon the expression).

She played with the Brindisi, as much as sang it. In my judgment, parts of “Ah, fors’è lui” were overly slow and overly milked. She was feeling her oats. But “Sempre libera” was rightly giddy and dazzling. Those keeping score at home will like to know that she did not go for the high E flat; but she’d sung a marvelous D flat.

“Non sapete” was hunted, desperate. “Dite alla giovine” was pure and heartbreaking. Violetta’s laments at the end of the second party scene were even more heartbreaking. “Addio, del passato” was oddly fast, but not without effect.

Overall, Ms. Fleming’s characterization was stunningly knowing. Those lucky enough to sit in the first rows – or to have good binoculars – saw a great many subtleties on her face. Seldom has Violetta’s self-sacrifice been nobler; seldom has her disintegration been more awful. Act III, by itself, was a tour de force.

Honestly, a good performance of “La Traviata” is almost unlistenable and unwatchable. The story is all too much. And, on Saturday afternoon, you could be forgiven for wanting to flee the building. It was almost impossible to take, thanks to Ms. Fleming – and others (Verdi, foremost among them).

Singing Alfredo was the American tenor Matthew Polenzani. When he first milled about the stage, I had trouble recognizing him, in his mustache and beard. But there was no mistaking the voice: It was fresh and sweet, gleaming and lively. If he continues to stray from Donizetti and Mozart – taking on heavier roles – will that voice retain its essential Polenzani-ness? Let us hope so.

He dispatched “De’ miei bollenti spiriti” almost too easily, as though this difficult aria were nothing. His later high C was like falling off a log. And he blended very well with Renée Fleming – in “Parigi, o cara,” for example.

Doing his familiar role of Germont was Dwayne Croft, the American baritone. As always, he was smooth, virile, and burnished. He gave no less and no more than we want in Germont. He is a most reliable performer. For this reason, I’ve always suspected, he is slightly underrated – underrated for his very reliability and predictability.

And I might point out that the veteran bass Paul Plishka was Dr. Grenvil – professional in his every move and note.

Those who care about nationality may have observed that the cast was all-American. The conductor was not: He was Marco Armiliato, born in Genoa, and he had a superb afternoon. From the opening notes of the prelude right through to the awful end, he was on-target – masterly, even. At every turn, he demonstrated what you might call musical and theatrical timing. I have heard this opera conducted by many more famous conductors; I have never heard it conducted better.

And, from the prelude on, the orchestra played sensitively, precisely, feelingly. The clarinetist outdid himself (herself?). And the Met chorus is not to be taken for granted, either.

It’s funny about opera, as about theater, sports, other things: Sometimes chemistry is there; sometimes it isn’t – at all. A week ago, for a Met “Zauberflöte,” nothing went right (except for Diana Damrau). In this “Traviata,” everything went right – the experience was overwhelming.

The production, of course, is Franco Zeffirelli’s, from 1998. Will it survive much longer in this new age at the Met? Mr. Zeffirelli is politically incorrect. Fortunately – for those who love this art form – he is operatically correct. His productions look and feel like the operas they serve – and serve is what they do. An age in which Mr. Zeffirelli is out of fashion is probably a tragic age for opera.