'The Voice' Winner Gina Miles and Coach Niall Horan Reflect on 'Crazy' Victory (Exclusive)

It was the closest margin of victory in 'Voice' history between Team Niall and his TV dad, Blake Shelton!

On his very first season of The Voice, Niall Horan stole a win from his TV dad, Blake Shelton!

The first-time coach pulled out a victory in Tuesday's season 23 finale, with his Team Niall singer, Gina Miles, beating out Team Blake's Grace West, in what host Carson Daly said was the smallest margin of victory in    Voice history.

Blake was angling for a record-extending 10th victory in his final season on the NBC singing competition, but this time, the student outshone the master.

"He said, 'I taught you everything you know!'" Niall laughed with ET's Cassie DiLaura backstage after the finale, recalling Blake's reaction. "That's not even a joke. It was such a special night for him, but it was also fantastic to kick that man out the door."

The victory came amidst star-studded performances and tributes to Blake's 23 seasons on the show, however, no one was more emotional than Gina when the news was announced.

"t was crazy, I just did not expect that," the soft-spoken 19-year-old singer told ET backstage after her big win. "I'm just so very grateful to be here." 

Still reveling in the moment, Gina was candid when it came to what's next for her. "I haven't slept in like, days, so I'm probably going to sleep and eat and call my dad," she shared.

And Niall had nothing but praise for his young star, and pledged to help her continue to further her career and keep this moment going.

"I can't think of a bad performance she's put in," he said of her time on the show. "It's tough out there. It's not easy for any of us. But I'm going to try and make sure that Gina gets looked after, get her in the right rooms, let her write from her heart, and see what happens."

ET spoke with Niall  -- who will officially be back for his second Voice season in the fall -- ahead of Monday's finale performance show, where he raved about Gina's talent, calling his shot and saying the gifted teen performer deserved the win

"She deserves to win it like the girl is so gifted she's 19 years old I think we're forgetting that too and she sings like that it's just insane to have such big controlled tone at that age is just nuts um and I asked the people of america when you're voting think about the future past this show um I think she's got a very very bright future this girl um fingers crossed for her

Niall also opened up about becoming fast friends with longtime Blake Shelton this season -- and bidding him farewell as he departs the show after 23 seasons.

"We're gonna have a few drinks, no doubt," Niall said with a smile. "I'm gonna miss him. Big time. I've made a real friend."

"Like, I didn't know the guy in October of last year, but he's just been a constant. We text every day. He's been a laugh the whole [time]," shared the singer. "I hope he doesn't win it! But I'm gonna miss him."

The Voice will return this fall for season 24.