One of the first and most important things to understand about The Natural is that the story is strongly based on Arthurian legends, particularly those of the knight Perceval and the Fisher King. To briefly summarize the legend, the Fisher King was an old king who had been deeply wounded as a child. Since a king is intimately tied to his lands, the king's wound became that of his kingdom's, and it became a barren, wasted land. Only the healing powers of the Holy Grail can restore the Fisher King's health—and, as such, the health of the land. One day, Sir Perceval, a pure but largely untested knight, comes across the Fisher King. Perceval witnesses a strange procession where a great cup is carried before him, but, believing courtly silence to be the best move, Perceval fails to ask the Fisher King the meaning of the procession. In his silence, Perceval loses an opportunity to heal the King, who is ultimately not healed until much later, when Perceval forgoes the rules of courtliness to succeed in the quest of the Grail.
In The Natural, Roy Hobbs is a kind of Perceval. Like Perceval, he is a young country bumpkin with a "natural" talent, but also with a preoccupation for the conventions that surround his area of expertise. Just as Perceval is too focused on the rules of courtliness and achieving fame as a knight, Roy is too focused on setting records and achieving glory as a baseball player. Like Perceval, Roy fails his knightly "test" when Harriet Bird asks him about his plans for the future. He tells her he is going to be the best the game has ever seen, but when she asks, "Is that all?" he has no other answer. Roy is unable to see beyond himself and his own desires or, at best, outside the game of baseball. He does not see himself as part of a larger system in which he is the vegetative hero-god who can rejuvenate the Fisher King (Pop Fisher) and therefore the Waste Land as a whole. The tragedy of Roy Hobbs is that he is unable to understand his gifts and how he is meant to use them until the very end of the novel, when it is too late. Most significantly, he does not grasp the fact that Memo Paris is a destructive force, while Iris Lemon offers him the best chance for a happy life. It is his childish lust for Memo that ultimately leads Roy to his downfall.
One significant aspect of Roy that must not be overlooked is his bat, Wonderboy. While the bat may seem counterintuitive to modern ideas of individuality and free will, Wonderboy is an essential part of Roy's ability as a natural. Roy is a "bad ball hitter," meaning he goes after poor pitches. As long as he is wielding Wonderboy, he can strike those pitches. Wonderboy is, like Arthur's Excalibur, a symbol of manhood, but it is also the source of Roy's special "psychic energy," as critic Ed Wasserman calls it. The Natural is more a romance than a realistic novel, and so Wonderboy can exist as this magical weapon. It is only when Roy misuses Wonderboy, firing angry foul shots at Otto P. Zipp while intending to throw the game, that Wonderboy fails him; one of Roy's foul shots strikes Iris Lemon, and then the bat breaks on his next hit. Just as Excalibur breaks when unfairly used by Arthur against the perfect Lancelot, Wonderboy does not bear its misuse.