The embarrassed judge had turned around for hopeful Linda J before she made the remark.
Having finished her performance, Linda received three red chair turns.
Will.i.am, Tom Jones and Gavin had all turned around for the singer.
However, Linda had no clue who 51-year-old judge Gavin was when she finally saw his face.
Linda said: “I don’t know whether to go for Will.i.am, Tom, or the other guy?”
Viewers could not believe that the contestants had not been briefed on the new judging panel.
Fans took to social media, but even they seemed confused on Gavin’s actual name.
One tweeted: “She actually just called him the other guy! Dying. Poor Tony #TheVoice.”
“Haha poor ‘other guy’ Gavin Rossdale. Come on Linda J! #TheVoiceUK,” posted another.
A third said: “‘…or the other guy.’ #TheVoiceUK wow.”
“Why doesn’t anybody know who Gavin Rossdale is?” questioned a fourth.