WATCH NOW: Rihanna on The Voice

Over the past couple of weeks, the season-nine coaches on The Voice had to make really tough choices during the Battle Round as they pit their own artists against one another. The Knockouts kicked off tonight, and the hard choices kept on coming, as the coaches now have to cut their teams in half before the next stage of the competition. To help both the coaches and the artists get ready for the Knockouts, global icon Rihanna came to The Voice as a key adviser.

Adam Levine’s team was up first, and Levine matched twins Andi and Alex Peot and with Blaine Mitchell, who is new to Team Adam after being stolen from Blake Shelton in the Battle Round. The twins chose to sing “Stupid Boy” by Keith Urban. Even though they usually gravitate toward a more indie folk sound, they chose a country song to try to showcase their versatility. “They have their own vibe,” Rihanna said of the twins.

But Mitchell wasn’t going to down without a fight, especially after narrowly avoiding elimination in his battle. He performed first with “Hold Back The River” by James Bay, and it was a dynamic performance that really built. But it’s hard to compete with the beautiful harmonies of the twins, who nailed their performance of “Stupid Boy” and showcased exactly what makes them such a mesmerizing duo. They were extremely different performances, which left Levine with a difficult decision, and he began the night with a surprise by choosing Mitchell. Levine clearly sees something special in him. The coaches only have one steal in this round of the competition, and no one opted to take the twins.

Gwen Stefani’s team was up next, and she paired 15-year-old Braiden Sunshine with Ellie Lawrence. Sunshine picked “Feelin Good” by Michael Bublé. His voice cracked when he was in rehearsal, but Rihanna assured him that he just needs to commit to the note if it happens and keep on singing no matter what. Lawrence decided to sing “Cool For The Summer” by Demi Lovato, and Rihanna pushed her to really dig into the song and hit it hard.

Stefani and Rihanna agreed that Sunshine needed a more grown-up look if he was going to take on this song, and in his performance, he showed off a revamped appearance inspired by them, slicking back his hair. But it wasn’t the makeover that made Sunshine seem older than he is; it was his unwavering, strong vocals. He gave one of the best performances of the night, making it a tough act to follow, but Lawrence gave a solid performance and looked very comfortable on stage. She just didn’t show the same level of growth as Sunshine did. Stefani picked him as the winner.

The next Knockout pairing came from Team Blake. Shelton paired Barrett Baber with Blind Joe. Baber chose “Colder Weather” by Zac Brown Band. In his rehearsal with Rihanna, she told him he needs to stop being polite in his performance and just really go for it. Baber showed significant improvement between their rehearsals and their performances, which is definitely how it should be at this stage of the competition as the coaching becomes an increasingly important factor.

Blind Joe decided to sing “Mammas, Don’t Let Your Babies Grow Up To Be Cowboys.” “You just took that song to different heights,” Pharrell said of his performance. But he also had a few pitch issues in the performance, and his nerves showed. Baber’s performance was just tighter overall, and Shelton chose him as the winner.

From Team Pharrell, Amy Vachal and Madi Davis were up next. Vachal sang “A Sunday Kind Of Love” by Etta James, and she, too, showed a lot of improvement from her rehearsal to her performance, deftly incorporating some of the advice Rihanna provided. But it was another tight Knockout, with Davis also giving a really strong performance that highlighted her strengths. She sang “A Case Of You” by Joni Mitchell. Her voice sounded beautiful, and Pharrell said he thought they were both winners. Still, he had to pick, and he ultimately went with Davis. Levine immediately pressed his button to use his only steal, but he wasn’t going to get away so easily. His rival Shelton went for his button as well, and the two coaches duked it out over Vachal. She chose to join Team Adam. Your move, Shelton.

Next, Shelton matched his two steals from the Battle Round, Chance Pena and Ivonne Acero. Pena decided to sing “Demons” by Imagine Dragons, and Rihanna and Shelton advised him to really open up his voice. Acero, who didn’t make it past the Blinds last season and who lost her battle this season, had a lot to prove. She did not let down. She sang “Part of Me” by Katy Perry, and she blew away Rihanna in her rehearsal. Tonight, she gave her personal best performance she has given on the show and finally conquered her nerves. Pena also gave a strong performance, but he just didn’t push himself in the same way Acero did. Shelton picked her as the winner.

The last Knockout of the night paired Jordan Smith and Viktor Kiraly from Team Adam. Smith, who has been surprising even since the Blinds, made an ambitious song choice, deciding to take on Adele’s “Set Fire to the Rain.” He let loose in his rehearsal and proved right off the bat that he has what it takes to sing a difficult, layered Adele song. Kiraly also made an ambitious choice with “If I Ain’t Got You” by Alicia Keys. They both ended up closing out the night with the best Knockout matchup. Smith and Kiraly both showed incredible range and commanded the stage. Levine was left with an impossible decision. He went with Smith, but it ended up working out with Kiraly, who was stolen by Stefani in the night’s final twist.

The artists who advance from the Knockouts will compete in the Live Playoffs later this season. Do you think the coaches made the right decisions tonight? Sound off in the comments, below.