The workrate argument is nonsense. We have seen since he left this to be the case. Koeman just didn't rate him. I've no idea why Martinez dropped him but I've heard he was a bit of a messer in training.
I'm not surprised Koeman didn't rate him but it doesn't mean he's a bad footballer and I suspect he will do very well at Barca next year.
Koeman and Martinez are polar opposite types of managers. There were very few of Martinez's players Koeman did rate.
I name thee beast as @Adversus.
You need to let Geri go, 5 managers have so far binned him off after 6 months, 5 different managers in 3 different countries.