Football match prediction using regression
If your MSE is low, but then your predictions on the test set are way off, i can think only of over-fitting either you're leaking information from the training set to the test set ( or vice-versa ) or you simply have a complex model ( too many features ) which you could solve by increasing your data or going for less features.

That's a first diagnosis, maybe you could plot your learning curves so you can check your variance/bias and tell which one of those problems you have.