No, it isn't too late at all. Actually, just about the right age. Just start with OB and play at the retrieving. Stress OB, nothing but OB, because that is what should have been done prior to this point. Throw bumpers every day but not as training, just as fun, perhaps a reward for good OB work. If you get on the OB hard and heavy then you can bring the dog back in line with a normal schedule in no time.