It’s always rewarding to see the understudy step in for the indisposed star, and become an “overnight” sensation. That is what happened at San Francisco Opera’s “Romeo and Juliet” earlier this month, when Samoan-born New Zealand tenor Pene Pati, who was scheduled to sing one performance, replaced Bryan Hymel for the entire run.

On Tuesday, I was able to catch a performance of the production, which opened the company’s 97th season in the War Memorial Opera House. I was partly interested because Cincinnati had the pleasure of being wowed by Pati in recital just last season for Matinee Musicale. But I was also interested in his Juliet — American soprano Nadine Sierra — who also performed a delicious recital for Matinee Musicale a couple of years ago. Since then, she has appeared at the Metropolitan Opera and won the 2017 Richard Tucker Award.

After the stunning performance by both of these artists on Tuesday, Cincinnatians can say, “We knew them when.”

Gounod’s lyrical opera (which was also performed at Cincinnati Opera last summer) was sung in French to a libretto by Jules Barbier and Michel Carré that closely matches Shakespeare. The production was by Jean-Louis Grinda and French-Canadian conductor Yves Abel led the opera orchestra.

Pati and Sierra, both former Merola Opera Program members and Adler Fellows, displayed a natural chemistry onstage and an ease of communication that instantly touched the listener. Both were making role debuts.

Sierra was enchanting as the young Juliet, as she twirled her nurse (Eve Gigliotti) while tossing off ribbons of coloratura with impeccable artistry in “Je veux vivre.” Later, she conveyed both terror and desperation in a tour-de-force performance of the Act IV soliloquy, as she took the potion given to her by Friar Laurence (James Creswell). Singing with a radiant tone from beginning to end, hers was as complete a portrayal as one could wish for.

Pati’s singing was the picture of elegance, and he remained fresh until his dying breath in Act V. Romeo’s famous cavatina, “Ah! Lève-toi, soleil” (“Arise, oh sun”) was deeply felt, a feat that combined both beauty of line and ardent, exciting top notes. His phrasing was consistently tender, seamless and utterly natural.

Gounod’s wonderful love duets were mesmerizing. The young lovers’ final duet, as they both lay dying, was both ecstatic and tragic.

Other musical delights in this production included Romeo’s charming page, Stephano (Stephanie Lauricella), who stole the show in the song, “Que fais-tu, blanche tourterelle” (“What are you doing, white turtledove”). And Lucas Meachem, as Mercutio, was entertaining in the ballad about the fairy Queen Mab, ““Mab, reine des mensonges.”

The chorus was excellent, particularly in the Prologue, recounting the tragic story of the lovers and their feuding families. I especially enjoyed the orchestra’s sound, which had wonderful presence in the excellent acoustic of the Opera House. Abel illuminated many wonderful details of the score, and propelled the music irresistibly.

During curtain calls, the “star-cross’d lovers” skipped out, holding hands and grinning broadly, to take bows.

Originally a co-production by Genoa’s Teatro Carlo Felice and Opéra de Monte-Carlo, the production premiered in 2012. The traditional scenic design (by Eric Chevalier) left me a bit cold, with its awkward raked stage. The fight scene had to be staged around an odd angle of courtyard arches.

For the final performance, October 1, the role of Juliet will be performed by Egyptian-born New Zealand soprano Amina Edris — Pati’s wife — marking a rare instance when a husband-wife duo will perform opposite each other in the title roles.

Pati makes an encore appearance with Matinee Musicale at Memorial Hall on May 3. Click here for information.