Fox announced Nicki Minaj, left, and Keith Urban as the two new judges on the upcoming season of “American Idol.” (AP)

With the unveiling Sunday of new judges Nicki Minaj and Keith Urban, “American Idol” has proved once again that those who sit at the judges’ table are more important to the show than the contestants who are increasingly relegated to the role of bit players.

“Idol” producers had long vowed to reinvigorate the show, which is poised to enter its 12th season in January amid sagging ratings. The magic potion? What else: a new slate of star judges, including popster Minaj and country crooner Urban. Minaj and Urban round out the judging foursome, which includes new addition Mariah Carey and her co-manager, “Idol” veteran Randy Jackson. Jackson was spared the axe after a failed bid to hire Latin singing star Enrique Iglesias.

Not long after last season’s “Idol” finale, with its traditional crowning of the Cute Scruffy White Guy with Guitar (Phil Phillips), attracted the smallest wrap-up audience in the show’s history, Fox execs promised investors and TV critics the show would undergo a shake-up.

And “shake-up” has come to mean bringing in a new crop of celebrity judges. (Host Ryan Seacrest has remained since the beginning.) “Nicki is someone who represents a different side of the music industry, who has now crossed into mainstream culture with her unique artistry, style and flair. Keith is one of country music’s true stars who brings with him charm, wit and knowledge about the industry,” said Cecile Frot-Coutaz, the chief executive of “Idol”-producing FremantleMedia, by way of explaining the new judges.

Last time “Idol” got a shake-up, when Jennifer Lopez and Steven Tyler joined the show in 2011, the fall was not so littered with like-minded TV shows and “Idol” enjoyed a ratings bump. In Lopez and Tyler’s second at-bat, however, ratings plunged 23 percent.

Snagging a new crop of celebrity singers as judges no longer ensures bigger ratings, as Fox’s other singing-competition series, the Simon Cowell-created “The X Factor,” learned last week.

After that show’s first season attracted far fewer viewers than Cowell and Fox had promised, “X” also underwent a highly hyped shake-up, in which judges Paula Abdul and Nicole Scherzinger were replaced by pop stars Britney Spears — at a reported salary of $15 mil a year — and Demi Lovato.

Wednesday’s second-season debut, in which Spears and Lovato were introduced and judged their first crop of auditioners, scored 4 million fewer viewers than Season 1’s disappointing kickoff. The next night, “X” fumbled away a few million viewers more.

“Idol,” which once had the singing-competition field to itself, now competes in a mature market — and at a disadvantage. For the first time, two other such shows — NBC’s “The Voice,” which has been moved to the fall, and Fox’s “X Factor” — will saturate the TV landscape from September through November, leaving fans of the genre sated before “Idol” has a chance to kickoff its 12th edition in January.

Not long after suits at the network and its parent company began promising a shake-up, Tyler and JLo announced in July they were bowing out of “Idol” and the network announced Carey had been signed, while declining to confirm the reported $18 million paycheck.

“Not being the only game in town now, we need to keep things fresh,” Fox programming chief Kevin Reilly said at the time.

Minaj’s and Urban’s names rose to the top in the past few weeks, from a pile of possibles that included Miley Cyrus, Kanye West, Nick Jonas, Adam Lambert, Katy Perry, Brad Paisley, Alanis Morissette, Sean Combs, Pharrell Williams and more.

The selection of Minaj, known for her neon wigs and goofy outfits, should not have come as much of a surprise to fans. When Minaj performed on the show last season, at one point she asked JLo to scoot over to give her a shot at guest-judging the show. Lopez replied frostily that there was not enough room.

Urban comes with actual singing-competition-judging experience, having played the part for one season of “The Voice” in Australia. Late last week, Urban announced he would not return to that gig next season, clearing the way to join “American Idol.”

Ironically, Jackson, who has been one of the judges on the show since its premiere in the summer of ’02, turned out to be the biggest surprise of the whole “shake-up”; he’d been written off as a judge by most industry pundits, although he’d been expected to stay in some “mentoring” capacity; he did, after all, play a big role in snagging Carey for the show in his capacity as her co-manager.

Fox finally made the announcement Sunday morning — the same day the judges’ round of auditions for the new season began in New York.

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