I always take Fotmob ratings for CBs and natural CDMs with a grain of salt. Those positions rarely score or create regular chances, yet they operate in the most high-risk areas of the pitch. If a CB consistently puts in a 6.5 to 7.0 performance, that is usually more than good enough.
What Fotmob does show well is when a player at those positions genuinely has a nightmare match. As VVD's 5.6 score reflects, he was atrocious, and the eye test backed it up completely. The first 30 minutes were easily some of the worst I've seen from him in a red shirthe made a massive error leading to a goal, looked slow and switched off, and gave away terrible passes.
Finally, Fotmob seems far better suited for evaluating EPL matches than Champions League ones. It's becoming increasingly clear that CL group/league play can often be loose or inconsistent, whereas the Premier League is tight, ferocious, and played at a relentless pace. In the EPL, where small margins matter most, Fotmob does a good job capturing the little things players do right (or wrong). With the overall standard rising so fast, I think the days of players racking up 3040+ goal contributions in a season are fading10+10 or 15+5 is likely the new benchmark for a great campaign.