This is why, when it comes down to it, I'd say squad needs a re-vamp. I'm not totally sold on Koeman yet. But, these arent his players. He's not been successful in getting a big reaction from this squad. Nice little start, but thats ebbed away. He has a responsibility for that. But it looks like a significant part of the squad aren't buying into it. And, as you point out, they are the common denominator really. If Koeman had been here 2 seasons and the squad was 'his' then he'd be on the chopping block. The players are in that position now. Who, out of them, truly wants to stay? They have to earn it if they do.Who has improved since year one of Martinez? I would say Lukaku and maybe Robles... not really sure there's anyone else.
Stagnated or worse: Coleman, Jagielka, Baines, Barkley, Deulofeu, Mirallas, Gibson, Oviedo, Kone, McCarthy, McGeady...
Seems hard to believe two very different managers could be entirely to blame...