Dustin Johnson heads into final round with one-shot lead

Dustin Johnson watches his tee shot on the 14th hole during the second round of the PGA Championship golf tournament at TPC Harding Park, in San Francisco. Picture: AP Photo/Jeff Chiu

Dustin Johnson has never been the easiest golfer to pin down. His physical gifts are undeniable. His mental acumen is, shall we say, unreliable. His inner desire is often unidentifiable.

There are days you wonder how Johnson hasn’t won a handful of major championships already. There are other days you can’t believe he won one at all.