The Maroon 5 frontman announced his departure from the singing competition after eight years in the role earlier this year, and whilst fellow coach Blake Shelton - who is the only coach besides Adam to have appeared in all 16 seasons of the NBC show - knew his pal was ''getting to the point'' of wanting to step away, he was ''pretty upset'' to discover he would be leaving this year.
Blake, 43, told 'Extra': ''I didn't expect it. I didn't expect Adam to pull the trigger like he did. ... We all knew he was getting to the point - it was 16 seasons he had been doing the show, and it's hard to keep him focused on anything. He was ready to move on. ... I was pretty upset that Adam was gone.''
But the country star won't be disheartened over Adam's departure for long, as his replacement is Blake's girlfriend Gwen Stefani, who coached contestants during three prior seasons of the show.
Blake said having Gwen on the show again will ''soften the blow'' of Adam leaving, but noted the dynamic will be different because he ''can't go head-to-head with Gwen'' like that he did with the 'Sugar' hitmaker.
Meanwhile, Adam's wife Behati Prinsloo recently said she's pleased he's left the show, as he will now be able to spend more time with his daughters Dusty Rose, two, and Gio Grace, 16 months.
She said: ''Good news for me, good news for the kids. He is on tour at the moment. He is excited to get home and for the first time have nothing to do. I'm like, 'What am I going to do with him?'''
At the time of his departure, 40-year-old Adam was claimed to have had the ''toughest schedules'' compared to his co-judges Blake, Kelly Clarkson, and newest addition John Legend, and so sources said the departure was ''bittersweet'' for the star as he now has more time to spend with his family.
Insiders said: ''Adam has always had one of the toughest schedules of the coaches. He's been ready to move on and also have more time with his family. It's bittersweet for everyone, but Adam is so excited that Gwen is going to take his chair. She's beloved by everyone at the show and at NBC.''