Daniel Brenna, as Siegfried, faces off against Fafner, the dragon/giant, in “Siegfried,” which opened Wednesday at the Washington National Opera. (Scott Suchman for WNO)

Catherine Foster, the British soprano, missed making her American debut singing “Hojotoho!” in “The Valkyrie” on Monday night due to a leg injury sustained during the dress rehearsal. Instead, she had to wait for Wednesday and “Siegfried,” the third opera of Wagner’s “Ring” cycle, in which her character, Brünnhilde, doesn’t even appear until Act III.

But she does, then, get a ravishing entrance borne on the full orchestra as she wakes from a 17- or 18-year sleep and greets the daylight with “Heil dir, Sonne!” (hail, sun). And Foster unsheathed a loud, clear voice that proved if not nuanced, certainly penetrating, as if determined to make the most of the moment.

There are a lot of ways to parse a “Siegfried,” and Francesca Zambello’s production, with Philippe Auguin’s conducting, continues to offer D.C. audien­ces a particularly rich ride. But one bottom line remains the two leads, and both Foster and Daniel Brenna, the Siegfried, were largely unknown quantities until Wednesday night (although Brenna sang the part of Alwa in the Metropolitan Opera’s “Lulu” last fall). Both proved more than respectable: Brenna, in particular, showed a savvy use of his voice, resisting oversinging in the first act, when he sounded pushed and bland, so that he was doing his best work in the third, unleashing a robust sound that made it clear that this singer is definitely someone to watch.

This “Siegfried” became one of my touchstones when it first opened in Washington in 2009, and it remains ­powerful. In Zambello’s dystopian vision of America, “Siegfried” depicts the world tipping toward disaster: the ­once-verdant planet scarred by industrial waste; its erstwhile leaders, Wotan and Alberich, now two homeless bag men swapping stories and delusions in an abandoned factory. This production’s knack for finding the drama in any given exchange was amplified by the relish with which the singers played these decrepit figures: David Cangelosi, as a Mime living in a battered trailer in a dump, almost stole the show with his exuberantly oily glee and self-delusion, conveyed with strong singing and even a few onstage cartwheels. Alan Held’s Wotan has become an old reprobate, baiting the other characters with a wise-guy enjoyment, and Gordon Hawkins’s Alberich had such a warmth and nobility that one keenly felt the tragedy of his position. I still don’t fully understand Zambello’s conception of the Forest Bird as a 19th-century youth buried in a book, a kind of daydream friend figure, but Jacqueline Echols sang the part with vividly rich sound. And Soloman Howard was a resonant Fafner, emerging from the innards of his dragon-machine to die before he can reveal to Siegfried the mysteries of his own origins.

If I sound slightly muted in my praise, it’s only because I am still dazzled by the magnificence of “The Valkyrie” on Monday night, which moved straight onto my lifetime list of greatest-ever nights at the opera. By contrast, “Siegfried” was merely very good. Auguin and the orchestra, who are emerging as the breakout stars of this memorable week, kept to the kind of understated subtlety that made some of the “Valkyrie,” in particular, so revelatory, but here didn’t have the same telling effect — at least in the third act. The key confrontation between Wotan and Erda that opens the act remained a little shapeless, set in a generic no-man’s land like the one that opened “The Rhinegold,” though Lindsay Ammann as Erda unleashed a striking, baritonal lower register. And the final scene always goes on too long. Foster, still visibly hampered by her leg injury, sounded a little generic herself, although she looked terrific and sang her highest notes with a gleam that glinted promise for “Twilight of the Gods.”

The first “Ring” cycle concludes Friday with “The Twilight of the Gods.” “Siegfried” will be performed twice more in the two remaining “Ring” cycles, through May 22.