Well I suppose it depends on how old the horse is.
If the horse is getting towards the end of his/her career and has been bred well then send to stud.
If the horse is young, 2-3 years old, and you feel he/she has the potential to win group races then put out to grass and let the horse have a chance in the future.
Black Caviar had a nasty lesion in the leg during 2010 and subsequently had to miss the majority of the season (Feb-Oct). Thankfully the trainer, Moody, realised he had a potential star and refused to retire Black Caviar and instead rested the horse.
Now look what Black Caviar has achieved, thank god they weren't hasty
