Doctors have not cleared Dale Earnhardt Junior to return to the NASCAR Sprint Cup Series as he continues to recover from a concussion.  As a result, he’ll miss at least two more races – Sunday’s Pure Michigan 400 at Michigan International Speedway and the Bojangles’ Southern 500 at Darlington Raceway on September 4th.  Alex Bowman, who drove the Number-88 Hendrick Motorsports Chevrolet to a twenty-sixth-place finish last month in New Hampshire, will make his second start as Earnhardt’s sub in Sunday’s race at Michigan.  Jeff Gordon, who has run the last four races in Earnhardt’s absence, will be back behind the wheel for the Darlington round on Labor Day weekend.