It was rather a lukewarmish opening the New York City Ballet provided last night for the start of its two-week engagement at the Kennedy Center, marking the beginning of what looks to be a whopper of a ballet year for Washington. There was, however, at least one aspect of the evening that deserves to be called sensational. This was the debut appearance, as Odette in George Balanchine's capsule version of "Swan Lake," of Darci Kistler, just taken into the company this past spring as a new member of the corps de ballet at the age of 15.

She's passed her 16th birthday since, but before that happened she danced as Odette, after coaching in the role from Alexandra Danilova, in a "workshop" performance by the School of American Ballet, the City Ballet's official training institution. Word came down that a young dancer of exceptional promise had stunned the New York dance wizards, and it's easy enough to see why. She's from Riverside, Calif., and very slight physically -- blondish, small-featured and wispy. But her proportions are those of the ideal ballerina -- long of leg and neck, compact in the torso, finely arched feet, all harmonious in contour.

There are lots of young dancers with splendid terpsichorean figures; the School of American Ballet seems to recruit a never-ending supply. But for Darci Kistler this is merely a starting point. The excellence of her training showed in every move she made last night, in her phrasing, the carriage of her head, her body placement, the melodiousness of her steps. All the rest -- and it's the rest that mainly stamps her as a dancer of awesome artistic promise -- is her own: the natural musicaltiy, the instinctive plastic fluency, the absolute self-possession (in the face of inevitable nervousness) and the expressive projection.

It was far from a finished performance she gave last night, and understandably so, of course. There were jerky pirouettes, edgy balances, phrases shaky in outline or hurried in articulation. But the lyrical purity of her dancing was never disturbed. Given a sensible husbanding of her powers, mastery would seem sure to follow.

Otherwise it was a decidedly low-key evening. There were no premieres, and no Balanchine ballets of the topmost class to help things along. The one Jerome Robbins work -- "Afternoon of a Faun," which is a masterpiece, to be sure -- was only partially realized. "Faun" is the most fragile of ballets; it's so much a matter of fleeting nuance. Ib Andersen, the company's new acquisition from the Royal Danish Ballet, danced beautifully, and with an animalian sensitivity that suits the piece perfectly. But though the lovely Heather Watts went through all the correct motions, she never really seemed to connect with Andersen, and the overall effect was one of calculation rather than sensual reverie.

The rest of the program consisted of the execrably tacky Balanchine-Robbins "Firebird," which not even the electricity of Kyra Nichols in the title role could save from ludicrousness and tedium; and a ramshackle performance of Balanchine's "Western Symphony," distinguished only for the lively contributions of Wilhelmina Frankfurt, Victor Castelli and Robert Maiorano in the first two movements.