Christina Aguilera decided to go with an 'American Idol' champion's song for a battle between Lily Elise and Cherie Oakley on 'The Voice' tonight. The two members of Aguilera's team had to face off with Kelly Clarkson's 'Since U Been Gone.'

Elise, a music-school trained singer, knew she had a big challenge in battling Oakley, who has toured as a background singer for a some major country artists.

"She's like the diva of country," said Elise of Oakley. 'So, the pressure's on."

"[It's] a type of song that has a lot of vocal range in it and some tough notes to hit," said Aguilera. "You have to have some lungs in your little body."

"I definitely feel a lot of competition," said Oakley in the middle of rehearsals. "Lily is nailing it."

Elise definitely seemed more intimidating when the two entered the ring, as she wore an outfit with a grey hood that made her look like a boxer. Oakley's country vibe definitely contrasted with Elise's soulful voice, but both singers held their own inside the ring.

During the deliberation, Oakley got to finally meet Reba McEntire, for whom she co-wrote a No. 1 country tune. When it came time for Aguilera to make her decision, she had a difficult time but she ended up choosing Elise. Unfortunately, the competition ends for Oakley.

Watch Lily Elise and Cherie Oakley Perform 'Since U Been Gone' on 'The Voice'