Amber Wagner as Leonora and Rafael Davila as Don Alvaro in the Washington National Opera's "The Force of Destiny." (Scott Suchman)

The ways of opera houses are inscrutable.

When the Washington National Opera opened its production of “La Forza del Destino” the other week, I tried to think of reasons officials engaged such poor singers. It’s almost impossible to find good Verdi singers these days, so they probably — I reasoned — simply couldn’t find anybody better.

Then I went for a performance Tuesday by the second cast and heard some of the best Verdi singing in years.

Why didn’t we hear these artists on opening night?

The singers weren’t all new to me, but I never heard them sound like this. I had heard the tenor Rafael Davila as Pollione in WNO’s “Norma” in March, so I knew he would be on the light side, vocally speaking, for the role of Alvaro. But I had no idea he could sing with such warmth, vigor and, often, beauty. As for Luca Salsi, he sang the role of Carlo with authority and considerable power, blowing away any memory of a time I had trouble hearing his lower register in “Un Ballo in Maschera” here in 2010.

I first heard Amber Wagner when she won the Metropolitan Opera National Council Auditions in 2007. It was my failure of imagination not to understand the potential of what I heard only as a decent, large voice.

That voice has blossomed into a promising Verdi soprano. All it lacks is a bit more bloom and fullness on the top; a couple of her climaxes were on the thin side, with a touch of stridency. But the ease, the rich low register, even some of the limpid quality that has marked the best Verdians were all in evidence Tuesday.

The other cast members were unchanged from the premiere, including Peter Volpe singing well as the doomed Marquis of Calatrava, who is killed in the first scene, and Valeriano Lanchas better than ever as the comic friar Melitone.

Good singing only enhanced Francesca Zambello’s production of the opera, which some reviews describe as neglected or misunderstood but remains a cornerstone of the Verdi repertoire.

“Forza” is about war, crowd psychology and human comedy. Strident contemporary references help bring across some of the points — and some of the feelings — Verdi was trying to evoke.

The only shift was in the quality of Xian Zhang’s conducting, which had declined from not-great to pretty awful. She conducted faster and more heedlessly, muddying details of the score and leaving the singers scrambling to catch up. She conducted with no evident sense of Verdi’s line or the emotional content of what was happening on stage above her. I could speculate that she had grown more comfortable with the score and therefore less careful.

I can also only speculate about the Washington National Opera’s casting choices. I can’t even say for sure who was responsible, because opera works on such a slow time line that most of the singers were probably booked years ago, even before WNO merged with the Kennedy Center.

Visuals might have played a role, because the opening-night soprano and tenor were thin, while Wagner and Davila are more solidly built. I could wonder whether some of them were not available for certain performances and whether Zambello’s team made any changes to the original cast, or tried to.

I only know that WNO assembled a real group of Verdians and only had them sing two performances of this wonderful opera. I’m glad I got to hear one of them.