The real reason Keith walked THE RED CARPET ALONE!

He claimed she had the flu, but friends say the singer was riding solo after a bitter fight with wife Nicole

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When Keith Urban arrived at the Grammys last week, awaiting fans and media were shocked to see he was on his own – with his wife Nicole Kidman nowhere to be seen.

And you can’t blame them – it’s rare to see him at music events without Nicole nuzzled into his side, providing photographers with countless public displays of affection.

But this time, Keith, 52, who was there to present an award, looked “out of place” without Nic, also 52, and seemed uncomfortable answering questions about her whereabouts.

“My wife is home with the flu,” he muttered to a reporter. “A lot of that going around.”

But once inside among the rest of the A-list stars, a witness says Keith let his guard down and told friends what was really going on.

“He seemed incredibly sad and distracted. It was clear something deeper was going on. He looked visibly distressed –kind of like a defeated man,” says one onlooker backstage at LA’s Staples Center.