Brace yourself, CBS executives, because if rumors of the cancellation of "Moonlight" prove true... There will be blood.

With only one day to go before CBS' upfront presentation to advertisers, reports slowly began filtering out on Tuesday (May 13) afternoon regarding the fate of the network's myriad bubble shows.

For fans of "How I Met Your Mother," "Rules of Engagement," "The New Adventures of Old Christine" and "The Unit," the news is good, according to the industry trade papers and Nikki Finke's frequently reliable Deadline Hollywood Daily blog. All four shows are expected to have homes on CBS' 2008-09 schedule when it's announced on Wednesday morning.

But for fans of the vampire soap "Moonlight" and the James Woods legal drama "Shark," there is no joy. Reports say that CBS has opted not to order a second season of "Moonlight" or a third season of "Shark."

"HIMYM," "Rules of Engagement" and "Old Christine" are integral parts of the network's Monday comedy block, though CBS had previous pointedly given renewals to "Two and a Half Men" and "Big Bang Theory," while leaving the other three sweating. Thanks to its "Men" lead-in, "Rules" has the biggest audience of the group with an average viewership of 10.75 million through last week. "HIMYM" had performed strongly since returning from its writers strike hiatus, while "Old Christine" was reportedly heading to ABC had CBS not ordered another season.

Averaging 11.3 million viewers per week, "The Unit" has been a solid success for CBS, but fans were given a scare when the network opted not to order post-strike episodes.

"Moonlight" fans, among TV's most rabid, will point out that their show was a regular time period winner in its 9 p.m. Friday home, fighting off competition that included NBC's renewed (with caveats) "Friday Night Lights." But with an average audience of 7.44 million, "Moonlight" usually lost more than a million viewers from its "Ghost Whisperer" lead-in and finished 1.6 million viewers behind its lead-out "Numb3rs." As a point of comparison, CBS cancelled last season's time slot occupant, "Close to Home," even though that legal drama averaged more than 10.2 million viewers.

Devotees of "Moonlight" had already organized a blood drive to demonstrate their dedication when the show's future was cloudy. It remains to be seen how they'll face cancellation.

As for "Shark," after averaging 13.58 million viewers last season in comfy confines post-"CSI," the show stumbled to an average of only 10.4 million airing on Sunday and then Tuesday nights.

CBS reps didn't respond to requests for confirmation or denial, preferring to let the network's schedule speak for itself on Wednesday.