Blake Shelton is leaving this year after 23 seasons on the singing competition — but he'll always have his memories with his best frenemy, Adam Levine.Blake gave the former coach a teasing shout-out during Tuesday's Battle Rounds when a contestant was faced with a unique situation. Neil Salsich had to perform his Battle solo, after Team Blake competitor Adam Whalen dropped out of the competition for personal reasons.«I told him backstage, if you lose this Battle, it will be the worst fail in history,» Blake said of his advice for Neil before his solo performance.