By Matt Hladik The NFL world is mourning the loss of longtime journalist John Clayton, who passed away on Friday after dealing with a brief illness. Clayton, who covered the league for over four decades, was only 67. He began his career covering the Pittsburgh Steelers in the 1970s before chronicling the Seattle Seahawks starting in 1986. Clayton was hired by ESPN in 1995 and spent 22 years at the Worldwide Leader, during which time he became a fixture to NFL fans for both his reporting and his professorial appearance. NFL commissioner Roger Goodell released a statement on Clayton’s passing th…