What symbolic elements in the quest for the Holy Grail appear in the novel, and what purpose do they serve?
In the Arthurian legend, the knights' quest for the Holy Grail was means to preserve and protect Christendom, the Holy Land, and its king. According to the mythology, a country bumpkin Sir Percival had a chance to heal the Fisher King and his kingdom, the Wasteland, with the redemptive powers of the Holy Grail. But, Percival remained silent as the Fisher King passed, refusing to intercede out of fear and weaknes.
In The Natural, the New York Knights are on a quest to win the Holy Grail of baseball, the pennant and World Series, in order to heal their team, city, fans, and--most of all--their manager Pop Fisher, who has been cursed by his infamous "Fisher Flop" earlier in his career. Roy plays the role of Percival, a combination of hero and bumpkin who, in the end, refuses to win the pennant and heal his manager. Instead, Roy falls victim to food, money, and women.
Malamud's novel involves a clash of mythology: the Holy Grail mythology battles the baseball mythology, Judeo-Christian mythology, and Celtic fertility folklore. Malamud seems to say that the modern hero can never live up to the ideal classical ones because of mass media, a lack of values and chivalry, and excessive pride and greed. In the end, the quest for the Holy Grail is corrupted as Roy chooses to pig out at Memo's buffet and take Gus' bribes.