The New York Times has a story about Rescue Me returning for its fifth season on Tuesday. Though it's much more focused on the show itself than the ratings, it did touch on them a bit:
Ratings for “Rescue Me” through its first four seasons were remarkably steady, with the first telecast of each new episode drawing between 2.7 and 3 million viewers. But thanks to the writers’ strike of late 2007 and early 2008 the show has been off the air for 18 months, the kind of hiatus that almost always diminishes a show’s audience.
FX has responded with several unusual votes of confidence: a supersize 22-episode order (a rarity for basic cable, where a season typically is never more than 13 episodes), a plan to run those shows over 22 straight weeks, a 10-city “Rescue Me” comedy tour headlined by Mr. Leary, and a commitment to a sixth season of 18 episodes, to begin in 2010.
I'll be very interested to see how it performs, but I don't think FX is likely using Damages as a benchmark for expectations. Damages drew around a million in its finale, but even for FX, it is not a show with broad appeal. A better benchmark might be Nip Tuck, which generally seemed to average between 2.0 and 2.4 million during its second half of its fifth season that ran from early January to early March. That might set set the high-water mark for FX at this point, and I'm guessing if Rescue Me performs within that range, FX will be ecstatic.