Selena Gomez, John Fogerty, Brad Paisley and Missy Elliott are all slated to become mentors of the four judges for the upcoming ninth season of "The Voice."

US Weekly reports Gomez will be Gwen Stefani's mentor; John Fogerty will be Adam Levine's; Brad Paisley will be Blake Shelton's; and Missy Elliott will be Pharrell Williams'. Season 9 premieres on NBC on Sept. 21.

According to US, the 23-year-old Gomez was a backstage favorite.

"She was surprisingly amazing as a mentor even though she's so young," a source said of the "Come Get It" singer. "She exceeded everyone's expectations."

Meanwhile, the 36-year-old Levine is rumored to have "always wanted to work with Fogerty" and considers the 70-year-old crooner a legend. "John performed at 'The Voice' finale and that's when Adam asked him to come back this season as a mentor," a source said.

Reports are Shelton and Paisley's relationship extends far beyond just the stage. With Shelton in the midst of a messy divorce from wife Miranda Lambert, Paisley is rumored to be a "good friend" to Shelton and has been helping him through some of his struggles.

The 44-year-old Elliott has worked with countless artists in arranging a number of mega hits and is known throughout hip-hop circles for her calming demeanor. She has worked as a producer or songwriter with the likes of Mariah Carey, Whitney Houston, Beyoncé, Janet Jackson, Christina Aguilera, Monica, Tamia and Ciara.

Mentors enter the fray during the competition's battle rounds, immediately following blind auditions. The foursome of Gomez, Fogerty, Paisley, and Elliott join an alumni class of award-winning performers who've served as mentors, including the likes of Lionel Richie, Alicia Keys, Meghan Trainor, Gavin Rossdale, Stevie Nicks and Ellie Goulding.