Why is it so hard to break into the NFL?

[Nickie]

As Louis Rees-Zammit becomes the latest 'crossover athlete' unable to make the NFL transition, BBC Sport looks at why it's so hard to break through.

More... (https://www.bbc.com/sport/american-football/articles/c78zeqwg0e0o?at_medium=RSS&at_campaign=rss)