The heavily promoted premiere of “Coupling” on Thursday could perhaps best be summed up as an initial disappointment for NBC.
   The show, a British import that resembles “Friends,” lost 21 percent of “Will & Grace’s” lead-in rating last night. “Coupling” had an 8 adult 18-49 rating at 9:30 p.m. and was the only NBC show that didn’t rank No. 1 in its time slot. It ranked No. 2 behind the second half of CBS’s “CSI.”
   Still, NBC ranked No. 1 for the night in the 18-49 demographic by a wide margin.
   The network had a 10.3 and CBS had a 7.6. ABC had a 2.3, Fox had a 1.9, UPN had a 1.5 and the WB had a 0.9. All ratings are based on preliminary data from Nielsen Media Research.
   NBC also ranked No. 1 in households with a 14.1 rating and 22 share. CBS had a 13.5/21, ABC had a 5/8 and Fox had a 3/5. UPN had a 2.5/4 and the WB had a 1.8/3
   NBC could take some comfort that it had a good premiere night. But the “Coupling” slump has got to hurt. The show has been touted as a replacement for “Friends,” at least in terms of keeping viewers tuned in on Thursdays. Because of “Coupling’s” relatively raunchy content it’s not expected to take “Friends’” 8 p.m. time slot when that show ends its run next May.
   NBC couldn’t even help “Coupling” by staggering its lineup. The network attempted to carry viewers from one show to the next by having its top shows straddle more than one time slot. “Coupling,” for instance, started at 9:27 p.m., following an extended version of “Will & Grace” that started at 8:48 p.m.
   That strategy has worked for NBC in the past and up until “Coupling” worked last night.
   An extended version of “Friends” had the night’s highest rating. It averaged an 11.1 at in its first half-hour. “Will & Grace” was the top show in the 9 p.m. half-hour and “ER” ranked No. 1 at 10 p.m. with a 10.4 rating.
   As it was last season, CBS was competitive throughout primetime.
    “Survivor: Pearl Island’s” rating dipped only 6 percent from its premiere last week, which faced repeats on NBC. “CSI” was No. 1, on average, in the 9 p.m. hour. And, perhaps most encouraging for CBS, “Without a Trace” ranked a solid No. 2 at 10 p.m. with a 5.8 rating.
  Meanwhile, ABC’s “Threat Matrix” is continuing what seems like an inevitable short run on Thursdays. Its already weak rating fell 24 percent from its premiere last week, to a 1.6. “Extreme Makeover” at 9 p.m. did better but its rating fell 16 percent week to week, to a 2.6.
   Fox was trounced with a two-hour “Temptation Island.” UPN was relatively competitive with “WWE Smackdown” and the WB’s revamped lineup was more or less nonexistent last night.