(Cover) - EN Showbiz - Adam Levine admits that "it's just hard" to see his The Voice co-judges Cee Lo Green and Christina Aguilera go.

The pair announced in September that they are not returning for season four of the TV talent programme. Shakira and Usher will be taking the musicians' place.

Although the panelists were reportedly feuding at one point, Adam will miss his comrades immensely.

"As much as I embrace and welcome the new artists, it's just hard because we spent so much time establishing wonderful chemistry with each other, and I'm going to miss those guys," he told People magazine.

"It becomes like a family, so it does kind of feel like they're leaving the nest. I will miss my brother and sister."

Adam is very much looking forward to the future despite the absence of his friends.

The Maroon 5 frontman can't wait to work with his new colleagues.

"I'm really excited to hang with [new celebrity coaches] Usher and Shakira," he said. "It should be really fun and different, and shake things up."

The Voice, with judges Adam, Shakira, Usher and Blake Shelton, will premiere in spring 2013. (C) Cover Media