As far as I know your horses' stats, both hidden and visible, are set from the moment they are born (or from the moment they turn two, not sure). So whether your horse runs at all, runs badly, injures itself, has a low rating, never wins, is overraced, etc. has no bearing at all on its' potential as a brood/stud (aside from being indicative of its racing ability and thus what it might pass on). I have retired two year olds who never raced who have produced champions; so from what I have observed your horses' 'genes' are set in stone and their career as a racehorse is only an indicator of what they might be able to do in the breeding shed. Or not, you know how unreliable breeding can be lol
As for nicking a grade three placing- as I mentioned above it doesn't have any impact on your horses' ability to produce winners.
Good luck with your breeding
