For a moment there seems real potential in the director Michael Mayer's concept, the Rat Pack "Rigoletto," as it has come to be known from the advance publicity and reporting. Mr. Mayer and his production team zap the story from 16th-century Mantua to Las Vegas of the early 1960s. As originally conceived, Verdi's Duke is a licentious ruler attended to by crude courtiers who procure him women and envy his power. To Mr. Mayer this practically screamed Las Vegas in the heyday of the Rat Pack.

His concept is hardly audacious. It is not even that original, since the director Jonathan Miller set his landmark "Rigoletto," first seen at the English National Opera in 1982 and much revived, in New York's Little Italy of the 1950s, with the Duke transformed into a mob boss.

But Mr. Mayer, who won a deserved Tony Award for his hypercharged directing of the musical "Spring Awakening," has brought theatrical flair to his operatic debut, and there are dynamic elements in this colorful if muddled and ill-defined "Rigoletto." Especially at the start, when Mr. Beczala sings "Questa o quella," brashly stating that this woman and that are all the same, and jealous husbands should back off.

Christine Jones's wonderfully ornate set depicts the casino against a back wall of beckoning neon signs. In Susan Hilferty's costumes the Duke's hangers-on wear tuxedo jackets in varying colors and patterns that compete for tackiness. When the Duke sings, sequined showgirls bearing huge feathered fans surround him. And Mr. Beczala, looking jaunty and loose, sings with ringing tone and ardor, accompanied deftly by the 33-year-old Italian conductor Michele Mariotti, who has a sure feel for the give-and-take singers need to shape a Verdi line. This was an excellent outing for the rising conductor, who made his Met debut last fall in Bizet's "Carmen."

Of course, for Mr. Mayer shifting the story to Las Vegas in the 1960s was no doubt the easy part. There are big holes in his concept, starting with the rather important character of Rigoletto, Verdi's hunchbacked, pitiable and tormented court jester, sung here by the admirable Serbian baritone Zeljko Lucic.

Just who is this Las Vegas Rigoletto? Mr. Lucic first appears milling through the crowd at the casino wearing a loud sweater. But what is his job? His role in the world of the Duke and the casino? We are never sure.

Mr. Miller made Rigoletto a bartender, a poignant idea. A lowly bartender in Little Italy, the butt of constant jokes who must also keep the Duke and his mobsters amused, is an apt equivalent to a modern-day jester. In an interview with The New York Times Mr. Mayer said that he had modeled Rigoletto on aggressive comics, like Don Rickles, who could crack Sinatra up.

But the vagueness of the concept undermines Mr. Lucic's otherwise affecting performance. He is an unconventional but compelling Verdian who does not have the classic mellow, Italianate baritone sound. Still, his voice is big and penetrating, focused and true. There is a smoky quality to his tone, with a slightly nasal texture that lends humanity to his singing. And his phrasing is supple and elegant.

At the end of the first scene in the opera as written, Monterone arrives at the court to denounce the Duke for having seduced his daughter. Mr. Mayer then makes a move that comes across as glib and potentially offensive. In another interview he said that he was worried that a curse, serious business in 16th-century Italy, might seem silly today. So he turns Monterone into an Arab sheik. But as conceived by Verdi, Monterone is a count, lower than a duke but still an aristocrat. Making him an exotic Arab marginalizes Monterone. When the bass Robert Pomakov, who sang the role, appeared in his sheik's garb, many in the audience laughed out loud. So much for lending new terror to the operatic curse.

The most moving episode of Mr. Mayer's "Rigoletto" comes in Scene 2. Instead of shifting the action to an alley outside Rigoletto's house, as the libretto indicates, Mr. Mayer keeps Rigoletto at the casino after everyone leaves and the lights are dimmed. As he thinks of his adored daughter, Gilda, whom he is trying to keep homebound and safe, Rigoletto is haunted by Monterone's words.

A lanky young man alone at the bar, nursing a drink and smoking, speaks up. It is the ominous Sparafucile, here the strong baritone Stefan Kocan. This is exactly the time and place at which a hit man might be likely to find business. Then, when Mr. Lucic sings Rigoletto's great monologue, "Pari siamo," comparing himself to Sparafucile (after all, they are both assassins, one using verbal barbs, the other a knife), he confides his thoughts to a bartender, who only half listens to this suffering man.

The scene in which Rigoletto meets Gilda, the brilliant soprano Diana Damrau, is beautifully staged. Rigoletto, in his floppy raincoat, and Gilda, in a sensible blue dress, look achingly vulnerable during their father-daughter exchange. Ms. Damrau sings the role radiantly, combining agile coloratura with plush, vibrant sound, the embodiment of youthful yearning and restlessness.