We're underperforming because of the manager's tactics, BUT I do have some sympathy for RM. Putting to one side his possession obsession, he is correct in saying that it's individual errors that cost us.
We have a squad of football players who get paid to do nothing other than play football, it's their full time job. Most of them will have been playing organised football since the age of 6 or 7 and for 10, 15, 20 years+ will have been coached by some of the best coaches around. They don't go from playing Sunday mornings, coached by little Johnny's dad, to playing pro football. It's reasonable to assume that all professional players can do the basics... They can pass the ball 10-15 yards accurately, their first touch should be excellent, they should be able to read the game well enough to know when and how to mark a player and when to run with that player, they can strike the ball towards goal with power and accuracy more often than not, and their fitness levels should be good. Time and time again, we see failings with these fundamental basics.
Russell Martin does not help with his tactical inflexibility. He absolutely needs to play to the strengths of the team and not to some misguided ideology of how perfect football should be played. However, it isn't his job to put the players through a remedial class to make them actual footballers. Russell Martin needs to fine tune and motivate. His system brings out the worst in the some of the players because they just aren't good enough. For all his faults though, I'm certain that his tactics don't include misplacing simple passes, getting dispossessed before taking a second touch, letting attackers through unmarked and playing the ball out of play for no reason.