CHARLOTTE _ His last top 10 came seven weeks ago at Bristol; it was only his fifth of the year – the fewest since his first full year in the Cup Series in 2000. To say Dale Earnhardt Jr. is frustrated is an understatement. In his second season with Hendrick Motorsports, Earnhardt Jr. has struggled mightily, failed to show improvement and has been subject to a crew chief change that clearly shook his confidence. With teammates Jimmie Johnson and Mark Martin smoking the competition thi...