[Ether]

@ngreen: I think you might be misunderstanding the problem at hand. Dan's computation is failing because he is trying to compute OPR with insufficient data, not because he's using the Normal Equations approach (square matrix).

I suspect what he is trying to do is get "real time" OPR estimates during the early stages of an event, before enough matches have been played to create an overdetermined system suitable for least-squares estimation.