The lesson of Heraclitus – that you can’t step into the same river twice – is one the Metropolitan Opera occasionally elects to ignore. Consider “Falstaff,” the learned yet effervescent comedy with which, after a career of tragedies, Giuseppe Verdi said farewell to the stage on the threshold of his 80th year.

For the 2001-02 season, the company had decided to retire Franco Zeffirelli’s classic production after 38 years. A supposedly A-list artistic team (whose identity the Met declines to disclose) was to mount a new one. Then the designs came in. According to Joseph Volpe, the Met’s general manager, they weren’t bad: “But why, I asked myself, would we give up what we have for that? As far as I’m concerned, ours is the best.”

So the company rebuilt Mr. Zeffirelli’s old designs from scratch, taking the opportunity to mount the final scene in Windsor Forest as he had conceived it, rather than in the shopworn cut-down version we all knew. The Oscar-winning costume designer Ann Roth came in to re-create the principals’ wardrobe, to resplendent effect. Tonight this true-facsimile “Falstaff” returns to the Met for its first revival. Once again, the brawny Welshman Bryn Terfel, appropriately larger than life, is heading the cast.

Antique as the show may look in our eyes, this “Falstaff” was regarded in its time as a landmark not only in opera but in the American theater. Though Leonard Bernstein was in the pit, the review in the New York Times ran under the headline “‘Falstaff’ Staged by Zeffirelli.” There was no denying that the set was literal – but sumptuously as well as subtly and tastefully so. Most of all, though, the show was alive, from the leads down to the last extra.

At the time, New Yorkers had seen a single other example of Mr. Zeffirelli’s work: the celebrated Old Vic “Romeo and Juliet,” starring a doll-like Judi Dench, barely out of school. Reviewing “Falstaff” for the Sunday News, John Chapman recalled that production shed “a new light, intellectually and physically, on the tragedy.” In “Falstaff,” he observed, Mr. Zeffirelli allowed “no one to dawdle, no one to pause, no one to pose.” “Everybody must be alive”- that word! – “and in character – which is not always true of operatic casts.”

In youth, the director’s reputation rested as much on his finesse with actors as on the lavish decor with which he is associated now. For the 2002 revival, the Met expected him back in person to give the action his inimitable finishing touch. For medical reasons, that didn’t happen. Though the performances that ensued fell somewhat short of revelation, they did have zest and brio.

“Falstaff is always ready to believe again, to start again,” Mr. Zeffirelli has said of the title character, a wily, down-at-heels, old, diseased and drunken scoundrel with minor standing in the aristocracy. Oh, and he is fat, too – legendarily so. “Each time he falls into the trap laid for him, but he never really gets very angry. An extraordinary character.” Like Peter Pan, Sir John Falstaff (Jack to his friends) refuses to grow up.

The Falstaff we see in opera is less the Falstaff of the Shakespeare’s history plays, where he was born, than the Falstaff of “The Merry Wives of Windsor”: Falstaff in love, or any rate on the make, romancing two of the merry wives for their money in identical letters. They compare notes and vow revenge, which takes the form of an afternoon dunking in the Thames and a midnight hazing in the forest.

The moment that stays with me from the Met’s revival in 2002 was a bit of business by Bardolph, Falstaff’s bibulous sidekick, played by the bantam French character tenor Jean-Paul Fouchecourt. In the first scene Mr. Fouchecourt made a brave show of standing up to Mr. Terfel’s portly Falstaff, only to be roughly tweaked by the nose and bounced off his belly like a cork off a kettledrum. Mr. Terfel went on to barnstorm front and center. But three years later, I still get a pang to think of the chastened Mr. Fouchecourt perched on a barrel off in a corner, massaging his nose and battered dignity. He returns this season: reason enough to see the show again.

Ah, but there is that other inducement: Mr. Terfel’s star turn in the title role. Last time around, truth to tell, it disappointed me a little. The tone was harsh and aggressive, the manner gruff. Vocally as well as theatrically, Mr. Terfel played a misanthrope and a bully, unacquainted with merriment, grouchy, no fun. But not for a nanosecond was he coasting.

There are many predecessors from whose books he might – with brass worthy of Falstaff himself – think of taking a page. Notable proponents of the role captured on video are the reserved, aristocratic Jose van Dam, the bouncy Donald Gramm, and Giuseppe Taddei (twice), who brings to the role the spirit of the commedia dell’arte. Others in the royal line may be heard but not seen on CD: Mario Stabile, closest to Verdi, a noble rhetorician; the princely Giuseppe Valdengo, Toscanini’s choice; Welshman Geraint Evan, devious and sly; Tito Gobbi, the frequent colleague of Maria Callas, and her peer; Dietrich Fischer-Dieskau, sounding every inch the intellectual; the burly Renato Bruson; the romantic Juan Pons, still at large.

But for me, the greatest Falstaff is a comparative unknown: Ambrogio Maestri. A performer of Falstaffian height and girth, he assumed the role in 2001, when the conductor Riccardo Muti and the Teatro alla Scala of Milan commemorated the centennial of Falstaff’s premiere. In two different productions, Mr. Maestri sang with the silken timbre and phrasing of a young poet in love. Where too often we hear dry patter, he unlocked ravishing melody. His delivery of the text was fizzy, and utterly natural. In the gloomy soliloquies, he was lightly tragic. Whether in mischief or in misfortune, he never lost his disarming innocence.

For all we know today. Mr. Maestri is a one-trick pony: In other Verdi roles sung for other conductors, his magic has simply evaporated. Mr. Terfel, on the other hand, has proven in an international career of nearly two decades that he is an artist, vocalist, and musician of vast range and sophistication. Whether he can efface memories of Mr. Maestri’s Falstaff remains to be seen. His take on the title role tonight may well be brand new. Even if Mr Terfel felt like stepping into the same river a second time, he is much too mercurial an artist to do so.

The season premiere of “Falstaff” will be performed September 23 at 8 p.m. at the Metropolitan Opera House (Lincoln Center, 212-362-6000).