Verdi’s “Otello,” at the Metropolitan Opera on Monday night, may have been a mixed bag, but Renée Fleming, as our heroine, was glorious. In a role that she has sung for many years, Ms. Fleming was in full, fine voice, projecting notes radiantly and shooting them to the upper reaches of the house with seeming effortlessness. Hers is not the ingénue Desdemona voice, not innocent like Herva Nelli, who sang the role for Toscanini, but rather a full-throated mature woman whose purity is all the more significant for its having lasted for some seasons.

Every scene in which Ms. Fleming appeared was enriched by her presence. In the love duet of Act I, she intoned a refulgent cascade of tones and was simply great in the two big numbers that end her life. “The Willow Song” was notable for its cleanliness and purity, with no resorting to the Caruso sob for this masterful artisan. But even better was the ensuing “Ave Maria.” Here, Ms. Fleming achieved a level of vocal perfection that stood out even during this superb portrayal. In fact, the prayer was so good that nobody screamed “brava” or applauded at its conclusion. This was a genuinely holy moment and it deserved — and received — total silence.

This performance as a whole, however, reminded one of that one night a season when a star comes from New York to a regional opera company. Ms. Fleming was so much better than everyone around her that the contrast was often difficult to process. This is sometimes written into the score; she is supposed to be producing rounded tones while the children’s chorus makes more equivocal sounds. But this quality gap should not be noticeable for the remainder of the piece.

Verdi wrote that Iago should be unobtrusive, should look like an average citizen, his evil difficult to unmask. But Carlo Guelfi took this direction too literally, offering a pale shadow of a manipulator, his villainy more of the Eddie Haskell variety. When he was alone and disclosed his true nature to his audience in the famous “Credo,” his singing was oddly dispassionate and anemic. It was a stretch to believe him to be a danger. Ronald Naldi as Rodrigo and Kristinn Sigmundsson as Ludovico were adequate, while Garrett Sorenson did fine in Cassio’s one significant scene. Only the Emilia of Wendy White was excellent.

Johan Botha took forever to warm his lusty tenor, not fully flexed until the middle of Act III. He did a good job of keeping his tendency to bellow in check, but never sounded in command, the one characteristic of Otello that is not negotiable. Mr. Botha is a South African; it would be interesting to know how he felt about appearing in blackface. Adopting the polar opposite approach to his acting from that of Ms. Fleming, Mr. Botha died like a hippopotamus on a National Geographic special, whooping and hollering ad libitum.

As the Italians say, the fish stinks from the head. Conductor Semyon Bychkov wasted his opportunity to lead one of the greatest orchestras in the world. From the first note of the opening storm to the deep undercurrents at the opera’s conclusion, Mr. Bychkov never really took control of his forces, producing along the way a rather sloppy accompaniment. Ensemble scenes, normally the Met’s forte, were confused and ragged under his direction.