Christina Aguilera may have been especially surprised by the news that "The Voice" co-mentors Blake Shelton and Gwen Stefani are dating.

The "I Turn To You" singer allegedly never thought that there's a possibility that Blake and Gwen could be involved in a relationship.

Being Blake Shelton's close friend, does Christina Aguilera disapprove of his relationship with Gwen Stefani?

Though it is unclear whether Christina likes the No Doubt vocalist for her friend, it has been reported that the "Candyman" hit maker didn't think Stefani would ever go out with Shelton.

"For his part, we're told Blake called Christina Aguilera last week -- before he hooked up with Gwen -- and told Christina he had 'a crush' on Stefani," TMZ reported.

"Christina's response offered little hope ... 'Ha, good luck with that.' Turns out Christina underestimated him."

It has been previously rumored that Gwen Stefani isn't thrilled that she has to leave "The Voice" to make way for Christina Aguilera next season.

"Everyone knows Christina thinks this is her show and she can swan in and out whenever she likes. She refers to Gwen as 'the substitute!'" a source told OK! Magazine, as quoted by Celeb Dirty Laundry in an earlier news report.

Though Gwen Stefani allegedly heard about the news of Christina Aguilera's "the substitute" diss, the No Doubt singer doesn't seem to resort to name calling.

Instead, Gwen purportedly intends to fight back by being the best female mentor "The Voice" has ever had.

"She knows Christina turns her nose up at her and she's been told about the 'substitute' jibe - and she has a few tricks up her sleeve herself," the source continued, as quoted in the news article.

"She plans on going out as THE only coach everyone wants back - the most memorable coach and 'face' of the show."