Evaluating players based on role continuity

What a player does on a football pitch from a pure on-the-ball event perspective, quantifies only a small percentage of their actual role or influence on a match. What a player does off the ball can often be the key to a good performance, allowing a player to enhance their on-the-ball metrics in the process. So this begs the question - how can you evaluate a player's performance if they weren't really all that involved in the action, but stuck to their specific role perfectly?