As American Ballet Theater moved into second casts and repeat performances toward the close of its second week of repertory at the Kennedy Center, the focus of interest shifted to the new faces in familiar roles.

Saturday afternoon, for example, Rebecca Wright made her ABT debut as Swanilda in "Coppelia," patnered by Kirk Peterson, who shortly before had danced his first and quite winning Franz with the company.Once a mainstay of the Joffrey troupe. Wright, who's been with ABT several seasons now, has the look of an imp-innocent that makes her a very credible Swanilda from the start. Tiny but technically deft. She brought a neat, crisp attack to this tricky role, and seemed very much at home with its soubrettish comedy.

In yesterday afternoons' "Giselle" with Eleanor D'Antuono in the title role, the part of Count Albrecht was deanced for the first time since his recent arrival at ABT by John Meehan, former principal of the Australian Ballet. Meehan has a lot going for him as the noble hero type. He's tall, dark and handsome, his dancing is sturdy and free of mannerism, and he's a reasonably effecient partner. In view of these advantages, one hoped for more of an imposing characterization than he seemed able to project.

It may be that Meehan, reticent and undemonstrative by the standards of this broadly drawn production of "Giselle," may not have turned in to the company's histrionic wavelength as yet. But even in its own terms, his Albercht wa on the pallid side, watery in the first act pantomine and lacking intensity in the Act II dancing except for a long, vivid dequence of entrechats. One look tells you Meehan has lots of potential, he needs, however, to find the spark and conviction that can give his dancing the impact it promises.

D'Antuomo was a technically polished but otherwise only moderately convincing Giselle. Nanette Glushak has acquire both assurance and depth as Myrta, though, and Cathryn Rhodes and Jolinda Menendez were uncommonly cogent as her attendants.

The Dance Exchange - the innovative, community-oriented creative dance center led by Liz Lerman - offered an evening of "works-in-progress" Friday evening in its commodinous new studio quaters on RHode Island Avenue, NW. There was, as might be expected, a dizzying diversity of style and material. Among the most intriguing items were a pair of sharply etched solos by Sandy Benson: an amusing, autobiographical fragment about the urge to dance by Vince Brown; and parts of Lerman's own new group opus dealing with male-female role concepts, including a marvelously droll slow-motion sequence of men donning shirts that pinpointed the unsuspected fascination of daily life.