Would you buy a horse that is pigeon breasted? I know this is a relatively uncommon fault, but I am not sure how acceptable it is for a potential sport horse. The horse in question is only two years old. Is this something horses often outgrow?
Bulky breast muscles and legs set under the body decrease the efficiency of stride and swing of shoulders, hastening fatigue. It may interfere with the front legs, forcing them to move to the side rather than directly under the horse. It can cause a rolling gait that slows the horses speed, especially at the gallop.
It should interfere little in the sprinting sports that need rapid acceleration. The inverted V of the pectorals are important for quick turns, dodges, and spins needed by stock horses.