Main bearing failure- photos

Hello,

Any ideas what has happened with this main bearing? We noticed metal flakes in the oil filter and decided to take a look. The rest of the mains are ok, engine was running fine for 600 competitive km.

Bearing Photo

Bearing Photo2

Looks like surface fatigue according to this guide from Mahle:

Engine Bearing Failures.pdf

Yup - any other signs of detonation or pre-ignition? Another cause may be incorrect bearing type for the application - were these OEM or proper competition bearings?