Rainsford is described as a very experienced big-game hunter. He has traveled the world and hunted most of the big-game prey allowed by legal restrictions (the story was written in 1924, when hunting was a more accepted sport). He has also written a bestselling book on his experiences and his knowledge of hunting, which the antagonist, General Zaroff, has read.
"I'll give him a trail to follow," muttered Rainsford, and he struck off from the rude path he had been following into the trackless wilderness. He executed a series of intricate loops; he doubled on his trail again and again, recalling all the lore of the fox hunt, and all the dodges of the fox.
(Connell, "The Most Dangerous Game," fiction.eserver.org)
Rainsford is in this respect the opposite of Zaroff; his hunting experience has not left him bored with animals, but instead respectful of their instincts and drive to survive. His knowledge of hunting allows him to put up a better fight against Zaroff than other people, but Zaroff still manages to track him down and lets him go to prelong the hunt. Rainsford also understands the mind of a "Beast at bay," and flings himself in to the ocean instead of facing Zaroff and his dogs.