Willy recalls his son's teenage years as an idyllic past. What evidence can we find to show that the past is not as idyllic as Willy imagines it to be?
Throughout Willy's memory scenes, he recalls a time when Biff was a blossoming football star. When Biff arrives home with a stolen football, Willy praises him and mentions that the coach will probably congratulate Biff for his initiative. Bernard then enters the scene to tell Biff that he needs to study for his upcoming math exam. However, Willy ignores Bernard by insisting that there is no way that Biff's teacher will flunk him because he has scholarship offers. Willy then insists that Bernard allow Biff to cheat off of his exam. Linda then enters the memory scene and mentions to Willy that all the mothers fear Biff because he is too rough with their daughters. Willy again represses the thought that his son is possibly abusive towards women.
Throughout Willy's memory scenes, Biff's actions reveal that he is a disrespectful, lazy thief. Biff steals a football, refuses to study for his math test, and Linda suggests that he treats girls with disrespect. Despite Biff's significant character flaws, Willy believes that his son was always destined for greatness in his disillusioned idyllic past.
Willy is living an illusion when it comes to Biff. Willy wanted Biff to be a big-time football star after high school, but that never came to fruition. Biff did not end up being a football hero. Biff ended up floating through his life thus far and not really making much of it. He was a disappointment because he did not live up to his potential. Willy does not want to face this reality, so he lives in the past and consistently brings up Biff's "football days." This reveals Willy's larger problem, which is that his entire life is an illusion. He thinks he is someone he is not. He is a failure, not the success he tried to make himself out to be.
As a child Biff became a thief, stealing footballs. He failed his math exam, feeling that he could either talk his way out of a problem, have his father talk his way out, or rely on his sports prowess to ease his way. When Biff discover's Willy's infidelity in Boston, all pretense of idyllic scenarios fall away.