Troy Maxson, a former baseball player in the Negro Leagues, compares much of life to a game of baseball. In baseball, players get three chances, and Troy often feels cheated because he has not gotten even a second chance to undo the mistakes he has made in his life. He sees a connection between his lack of opportunity and the color of his skin. He wants to protect Cory from making the same mistakes he made, including playing sports:

Troy: "The white man ain't gonna let you get nowhere with that football noway." (1.3)

This is why Troy becomes so angry with Cory when he finds out Cory has lied to him about working at the A&P. To Troy, being a black man in America does not equate to having a fair chance at one's goals, so Troy wants Cory to focus on making a living rather than dreaming about football. In Troy's own way, he is trying to protect Cory from being let down. Cory ignores Troy by staying on the football team instead of focusing on working, and when Troy find out, this is his "first strike."

The "second strike" Cory makes with Troy comes when Cory stands up for his mother after Troy has a baby with Alberta. Rose, his wife, is upset with Troy's selfish choice to know other woman and when she confronts Troy about this, a fight ensues and becomes physical. Cory sees this and sneaks up behind Troy, knocking him to the ground. Troy tells him to not "strike out." It is significant that Cory had the strength to stand up to his father. It reflects Cory's ability to make his own choices, like quitting the A&P.

Six months later, Cory makes his third and final strike, which results in Cory leaving his father's house for good. Troy is sitting on the steps, blocking Cory's way, and Cory tries to get past him. Cory does not say excuse me to Troy, and a violent fight begins between them. The fight ends with Cory picking up Troy's bat and attempting to swing at Troy. Troy is able to take the bat away from Cory and tells him to leave. 

Cory's strikeout can be seen as his way to finally get past Troy's controlling hand and make his own life for himself.