After a month of repeats, CSI returned slightly lower in the ratings despite an eagerly anticipated cameo appearance by former star William Petersen.

CSI delivered 13.8 million and a 3.0 preliminary adults 18-49 rating, down 9 percent from its last original episode back in early January (video of Petersen’s return here).

The crime procedural wasn’t the only show with ratings in the red last night, however, with most shows posting declines. Increased competition likely played a role, since, for the first time since the start of 2011, every broadcaster aired first-run episodes across the board. Fox led the night with a steady American Idol (21.8 million, 7.5). Bones (10.2 million, 3.3) was down 15 percent from last week’s high now that CSI is back.

CBS and ABC tied for second, with CBS also airing Big Bang Theory (13.8 million, 4.3) and $#*! My Dad Says (10.5 million, 2.8), the latter up 22 percent this week. At 10 p.m., The Mentalist (15.1 million, 2.8) was steady.

ABC’s Wipeout (7.9 million, 2.5) perked up 4 percent, while Grey’s Anatomy (11.1 million, 4.2) was nearly steady and Private Practice (7.1 million, 2.6) slipped 4 percent.

With the exception of a steady 30 Rock (4.8 million, 2.4), NBC’s comedy declined across the board: Community (4.3 million, 2.0) down 9 percent, Perfect Couples (3.1 million, 1.4) down 18 percent, The Office (7.3 million, 3.7) down 8 percent, Parks & Recreation (5.1 million, 2.5) down 17 percent, and Outsourced (3.8 million, 1.8) down 5 percent.

Vampire Diaries (3.2 million, 1.4) was down 13 percent in the adult demo (but managed a 4 percent climb in the network’s women 18-34 target demo) and Nikita (2.4 million, 0.9) fell 18 percent from last week’s midseason premieres.

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‘CSI’ scoop: Marg Helgenberger talks about her contract, her TV boyfriend and William Petersen