LOS ANGELES –  With four wins, Blake Shelton is top dog among "The Voice" mentors. The competition begins again in earnest when the series returns for its ninth season on Sept. 21 and Shelton -- along with Adam Levine, Pharrell Williams and Gwen Stefani -- will be pulling out all the stops.

But despite his success, Shelton acknowledges that each season is a crap shoot, .

"I gave up Craig Wayne Boyd the year he won," the Academy of Country Music award-winning singer tells FOX411. "Luckily, I was able to get him back again. But that shows you, you never know who it is going to be and why it is going to be them. There is always that moment that will happen every season that will change everything for somebody, and it will shake up the whole competition. It's almost always somebody you didn't expect."

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With eight seasons behind him, Shelton says the one exception was Sawyer Fredericks, who last season had all four chairs -- Adam Levine, Christina Aguilera, Pharrell Williams and Shelton -- turnaround when he performed his blind audition.

"We all knew Sawyer was special from the beginning," Shelton says. "There were a couple of minutes, though, when Koryn [Hawthorne] was blowing up.  It was, 'Oh, no. She's the one blowing up here.' I think it is that moment that you just can't plan on."

Fredericks wasn't one of Shelton's four wins. They were Jermaine Paul, Cassadee Pope, Danielle Bradbery, and the aforementioned Boyd. But in thinking about why Shelton may be so successful as a mentor, the answer could be as simple as he had one himself when he was starting out.

"Trace Adkins was that guy for me …. unfortunately, because he's a grumpy, old bastard," Shelton jokes. "But he was always that guy for me who would set me down and say, "Listen," and he would get on to me about stuff. Especially because back in the day, I was way worse than I am now. He was about the only guy I would listen to because I was intimidated by him. Looking back, I am so glad that he was around for me."

And because he had someone who looked out for him, Shelton tries to pay that forward, especially for the members of his team to whom he gets attached.

"It's not all of them," he says. "There are some people who have been on my teams over the years that I never see or talk to again. There are some people you have a connection with and some you don't, but the ones I've had a connection with, I feel a responsibility to them -- just on a friendship level. Since I am in a position to help them, I am damn sure going to at least try."

Examples of that help include Shelton's recording a duet with his onetime "Voice" protégé Gwen Sebastian, or taking Dia Frampton on tour as his opening act. 

"She's the furthest thing from a country artist on the planet, but she needed a tour, I had a tour," he says. "She's my friend, so I brought her out. That's just how you do it, I feel like, if somebody is a friend."

And Shelton is hoping that his own friends will help him out in similar fashion. It's already been announced that Brad Paisley will be joining him in an adviser capacity for Season 9, but it remains to be seen who else might drop by.

"I always shoot for the moon, but you don't always get them," Shelton says. "I threw out Cher's name one time and she actually came and did it. I haven't been able to get Dolly Parton yet. Do you think she would come and do it?"

Now that Parton has a deal with NBC, which is producing a movie about her early life, "Coat of Many Colors," airing Dec. 10, she just may.

"The Voice" premieres its ninth season on September 21, 2015 on NBC.