Up until this year in his career, Juan Cruz averaged about 8.4 K/9.

This year, he’s at about 12.3.

Did he learn a new pitch or something?

Not that I’m aware of. He has been used exclusively as a reliever this year, and his appearances and innings have been very closely monitored to keep him healthy, as he is prone to sore shoulder and back strains. 

He has been very consistent with his velocity, 96-97, and has had better command of his slider than his walk totals would indicate.