Star power, after all, is what judges add to TV talent shows that otherwise feature unknowns whose performances can range from surprisingly good to stunningly awful.

But Fox’s ‘American Idol’, trying to right itself after shedding viewers in its 11th season, may also need to play a numbers game — as in the age of the judges brought in to revitalize a show whose audience is getting smaller and older, neither a plus for advertisers.

“They need judges who will resonate with young people,” said media analyst Brad Adgate.

Carey, Dion and Blige, undeniably winning stars, all are in their early 40s.

The median age for the ‘American Idol’ audience rose above 50 last season, the first time ever, and Adgate suggests it take a page from ‘The X Factor’ playbook, as devised by its creator and producer, Simon Cowell.

“Cowell beat them to the punch” by hiring Britney Spears and Demi Lovato after ‘X Factor’, the Fox version of Cowell’s British hit, stumbled in its debut last season. Spears, 30, and Lovato, 19, replaced Paula Abdul, 50, and Nicole Scherzinger, 34.

(Worth noting: The male judges, Cowell, 52, and producer Antonio “L.A.” Reid, 56, are staying put for season two.)

Lopez announced her departure on Friday, a day after Tyler (an unlikely senior statesman at 64) said he was leaving ‘American Idol’ to concentrate on his role as Aerosmith’s frontman. Both appeared for two seasons.

“I honestly feel like the time has come that I have to get back to doing the other things that I do that I’ve put kind of on hold because I love ‘Idol’ so much,” the 42-year-old actress-singer-dancer told ‘Idol’ host Ryan Seacrest on his radio show.

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