What’s at stake: NBC looks to keep the “Friends” flame lit awhile longer with Matt LeBlanc starrer spinoff “Joey,” which takes on Fox’s transplanted teen sudser “The OC.” Both skeins will have to contend with CBS’ surprisingly durable “Survivor” franchise, which is back for a ninth edition.NBC perspective: Its Thursday foundation has cracked some in recent years, but the likable “Joey” could help the net remain on top for the night in the key young-adult demos if it delivers roughly 70% of what “Friends” had been generating in the timeslot. Like its progenitor, “Joey” should be a broad performer for NBC, winning its slot in adults 18-49 and faring best among women 18-49, especially the younger half of the demo. Fox perspective: The net, which has been a speck on the rear-view mirror of NBC and CBS on Thursdays in recent years, is making a bold move by shifting “The OC” to lead off the night. Show fared well on Wednesdays in its first season but really didn’t put up great numbers until it was positioned behind “American Idol” halfway through the season. Now off on its own and asked to compete against “Joey” and “Survivor,” “The OC” should win its hour in teens but will be hard-pressed to come in better than third in most key ratings categories. Bottom line: Fox will improve its standing with “The OC,” but the net’s patience may be tested if numbers drop too much and the show loses its buzz. “Joey” isn’t expected to be another “Friends” for NBC, but the net is counting on enough of the longtime laffer’s viewers to stick around for a show whose pilot, at least, has hit potential.