McWhorter was an All-SEC guard at Georgia in 1973. McWhorter retired following the 2010 season with the Longhorns. The American Football Coaches of America voted Longhorn offensive line coach Mac McWhorter the top assistant coach in the country for 2008.
After spending 2011 out of football following his retirement at Texas, Penn State's new football coach Bill O'Brien convinced McWhorter to join the staff at Penn State, following the death of Joe Paterno. McWhorter, who one sportswriter described as O'Brien's "biggest get" onto the coaching staff at Penn State, despite his enjoyment of retirement and attending football games as a fan of the Georgia Bulldogs, agreed, and moved to the northeast for the first time in his life. His tenure at Penn State was not expected to last particularly long for a variety of reasons including parents in worsening health and grandchildren, but while at Penn State, he was beloved among his players, including offensive guard Miles Dieffenbach, who commented,
"We love him a lot ... He loves to have a good time. He's a funny guy. I don't know how old he is, but he's out there like he's 25 years old."
McWhorter noted that he loved coaching at Penn State, but had no timetable for how long he would coach. McWhorter retired following the 2013 season once again after not being retained by James Franklin.
"I thought it might be a great way to finish a career."