The final set of contestants who will complete the coaches' line-up will be revealed in this week's installment of "The Voice" season 9.

For the ninth and 10th episodes of "The Voice" season 9, celebrity mentors return to help coaches Blake Shelton, Pharrell Williams, Adam Levine, and Gwen Stefani train their remaining contestants who will complete their line-up for the upcoming Knock-out round. The mentors include American country singer Brad Paisley for Team Blake, "Get Ur Freak on" rapper and Grammy Award-winning hip hop star Missy Elliot for Team Pharrell, Creedence Clearwater Revival lead guitarist and singer John Fogerty for Team Adam, and pop singer Selena for Team Gwen.

During Monday night's battle, Adam, Gwen, and Blake all used their steal powers to get the losing contestants from another team. This means that only Pharrell's steal can save a losing contestant for Tuesday night's episode.

Blake pitted Blind Joe against Blaine Mitchell for the episode 9's battle competition, where the duo performed "Old Time Rock and Roll." While Blake chose Blind Joe to advance, Adam came to the rescue and saved Blaine for the Knockouts next week.

Adam, on the other hand, chose to pair Viktor Király and Cassandra Robertson to sing "Nobody Knows" by Kevin Sharp. But Viktor captured Adam's attention during their performance, which is why he had to let Cassandra go. However, Chance Peña got another chance in the competition when Blake decided to save him until the next round.

Gwen also had to say goodbye to several members of her team, when Braiden Sunshine outperformed Lyndsey Elm during their performance of Howard Jones' "No One Is to Blame" and Korin Bukowski won the battle against Chase Kerby after performing the song "Samson." Pharrell also had to let go of Riley Biederer when he chose Evan McKeel to advance in the competition, but Gwen opted to save Riley.

For Tueday night's Battle rounds, Blake pits Cole Criske and Nadjah Nicole against each other to sing "Rude" while Emily Ann Roberts and Morgan Frazier are tasked to sing "Temporary Home" to determine who will fill the final two slots on his team.

Pharell chose Beyonce's anthem "Single Ladies (Put a Ring on It)" for Daria Jazmin and Darius Scott and BeeGee's "To Love Somebody" for Amy Vachal and the newly engaged couple Jubal and Amanda to vie for his last remaining slots for the team.

Both Adam and Gwen only have one set of contestants for the upcoming episode before their teams are filled. For Adam, Shelby Brown and Amanda Ayala will perform Lonestar's "Amazed," while Gwen's ladies Summer Schappell and Hanna Ashbrook will perform Rachel Platten's "Fight Song."

All these performers will also attempt to get Pharrell's final steal for the Battle rounds to advance to the next level of the competition.

"The Voice" season 9's two-part episodes air Mondays and Tuesdays on NBC.