Christina Aguilera sang an UNBELIEVABLE rendition of the "Star-Spangled Banner" during Super Bowl rehearsals -- one of the best ever -- and she was so confident in her performance, she didn't even finish the song!!!
TMZ obtained footage of the National Anthem rehearsals -- shot Saturday in Cowboys Stadium.
Christina not only gets all of the lyrics correct -- but the delivery was Whitney Houston-esque.
So much for the maxim practice makes perfect ...
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