Of course, Donaire will take it seriously as he can't afford to lose the opportunity to have a rematch against Inoue, if he loses, I doubt Inoue would still give him a rematch when he doesn't have the belt anymore, it will be Casimero vs Inoue if Casimero would be successful in defending his belt.
Donaire still has it he doesn't have a long lay off and he is still fresh in his win against Oubaali he can take that momentum to this fight against Graballo, Donaire is so good in his counterpunch so we will see those counter punches against Graballo, but we cannot underestimate a fighter like Graballo who can hurt his opponent and I even saw some of his fights where he knocks out his opponents with one single punch, this guy is dangerous.