Author Dave Zirin covers the controversial union of sports and politics in his new book "Game Over: How Politics Has Turned the Sports World Upside Down."

Sportsmen during the Civil Rights movement and the Vietnam War never thought twice before revealing their political influence. While in some cases it brought about national changes and worked in favor of the athlete, in other cases it isolated them from their fans. However, according to author Dave Zirin, athletes have now fallen shy of expressing their political views. Advertisements and endorsements are two of the major reasons Zirin cites for this change.  

Zirin reveals that sportspersons of today refrain from taking a political stand because they have become more "sophisticated" in handling social media or any other media beyond sports which they feel they can't trust. Hence, they feel they are not in a position to speak directly to their fans about a matter they care about.

"Sports has become a trillion-dollar global entity by projecting athletes, really, who are as bland and apolitical as possible so they don't offend anybody in the audience," the author says. "So you're talking about a very limited window where athletes can earn the majority of money that they're going to make over the course of their entire lives. ... [Political speech] becomes something that actually is very dangerous, whether for keeping their job in the league, whether for keeping sponsors. And you do run that risk of finding yourself all of a sudden out of a job."

According to the author, college athletics may be the next stage of political dissent. "The NCAA tournament is an $11-billion deal all by itself. Coaches make millions and the players don't see a thing. This is one of those things where I really do believe that the center will not hold. Because coaches keep getting paid more and more, players more and more are seeing the NCAA as really this amoral tool of enforcement, like something that has no real moral weight."