season 20 Battle Rounds kick off next week, and substitute coach Kelsea Ballerini already has a tough call on her hands!Kelsea is standing in for pal Kelly Clarkson, who was sick during the filming of this season's battles, and, with input from Kelly, she paired up Gean Garcia and Ryleigh Modig for an impressive cover of Ariana Grande's «pov» in ET's exclusive clip from Monday's episode.Both young singers wow the coaches with their range and stunning runs.