You can't add work rate to a players game. It's a myth you can make someone work harder in any job because ultimately, they eventually revert to type when the threat of losing your job abates. That's especially the case when you can't sack them and they earn millions a year, unlike the real world.
You can make players fitter, give them a system to play in and direct their ability and drive but if they lack either, they're just not good enough to play at the top level. Too many in the squad don't have either (or both) the talent or the drive. It's that simple. If we put the entire squad up for sale today there's a handful who would interest any top sides.