‘The Voice’ Knockout Rounds: Rihanna Helps Send Early Favorites Home (VIDEOS)

Last night was the first round of knockouts for season 9 of "The Voice." This year the talent competition show brought in Rihanna as a special guest adviser to help the contestants prepare for the final round before the live shows. The episode featured some of the most intense battles and even a few premature departures from early favorites.

In the knockout rounds, a contestant is paired against a teammate once again, but this time, they get to choose their own song while their competitor watches and waits. Their coach must make a decision between the two performers. The artist that was not chosen as the winner by their coach is then available to be stolen by another coach. Each coach can only use one steal in the knockout round.

The night kicked off with Team Adam Levine, as the Maroon 5 singer paired up the identical twin duo Andi & Alex with rocker Blaine Mitchell. Andi & Alex were early favorites who earned a four-chair turnaround for their blind audition, while Mitchell was stolen by Levine in the battle round. Andi & Alex chose a song that was not necessarily in their wheelhouse, "Stupid Boy" by Keith Urban, while Mitchell chose "Hold Back the River" by James Bay.

The performance by the twins was the first time the two sang solo, and the performance was not as good as when they harmonize together. Mitchell nailed his version of the song after Rihanna called him "ballsy" in rehearsals. Both Blake Shelton and Pharrell Williams thought the rocker had "a real moment" on the stage, which meant the early favorites Andi & Alex were sent home shockingly early.

The next contestants up were Braiden Sunshine and Ellie Lawrence from Team Gwen Stefani. The 15-year-old Sunshine lived up to his last name and performed an impressive and upbeat version of "Feeling Good" by Michael Bublé. The voice of the youngest singer in the competition kept cracking in rehearsals, but with a little makeover help from Rihanna and Stefani, the teenager came out of his shell and even made Williams scream "wow" when he was done performing.

Lawrence was more of the favorite coming into the knockout round and chose to perform "Cool for the Summer" by Demi Lovato. Her performance was good but a little flat at some points and not as strong overall as Sunshine's performance. Stefani chose the 15-year-old over Lawrence.

Up next was Team Blake with his pack of talented country singers. Shelton paired up Barrett Baber and Blind Joe for one of the more evenly matched rounds of the night. Rihanna went absolutely crazy for Blind Joe's rendition of "Mamas Don't Let Your Babies Grow Up to Be Cowboys," and Williams even told him he took the song "to different heights."

For his time on stage, Baber chose to sing Zac Brown Band's "Colder Weather," a good choice for him. The high school drama teacher sounded like a seasoned professional, and the only advice Rihanna had for him was to just "go for it." In the end Shelton chose to go with Baber over Blind Joe.

The first knockout round battle for Team Pharrell was between Amy Vachal and 16-year-old Madi Davis. The two had a lot in common, according to Williams, who was excited about both girls' "other" quality. For her song, the teenager chose to sing Joni Mitchell's "A Case of You." Rihanna was surprised by her "rich tone," while Williams called her "a true artist." Davis was one of the more impressive contestants of the night and sang the quiet and loud moments of the song beautifully.

For her knockout performance, Vachel chose "A Sunday Kind Of Love" by Etta James. Vachel, like Davis, brought something different to "The Voice" and breezed through her jazzy rendition of the song. Rihanna suggested that Vachel sex up her performance and lose herself in the music.

While the battle between Vachel and Davis was intense, Williams chose the 16-year-old over Vachel. Before host Carson Daly could even announce that Vachel was available to be stolen, Levine pressed his button and gave fans of the show the first steal of the knockout round. Vachel became a member of Team Adam.

The most impressive knockout of the night was saved for last. Levine paired two of the strongest singers in the competition, Jordan Smith and Viktor Király, against each other. The two already had gotten a lot of attention from all four coaches, and both turned around all the chairs in the blind auditions. Smith chose to take on "Set Fire to the Rain" by Adele, a song that scared both Levine and Rihanna. After he finished his performance he left all four coaches staring at him in amazement after he hit a Mariah Carey-worthy high note at the end of the song. Shelton even said he thought it was one of the best live vocal performances he had ever heard.

For his performance, Király chose to sing a powerful song, "If I Ain't Got You" by Alicia Keys. The singer jazzed up the song a little bit, and like Smith, he took a song by a powerful diva to the next level. After the two faced off, Levine declared it was impossible to choose between the two, but he was forced to make a tough decision. In the end he picked Smith and his performance of "Set Fire to the Rain" over Király.

While Williams chose Smith, it was not Király's last performance on "The Voice" stage. Stefani swooped in and stole him, making him a member of Team Gwen.