He was quite perturbed because of the slow play, which this event is notorious for. It didn't help that his amateur player (Gretzky) had to WD over the weekend because of a bad back, leaving them playing as a threesome behind everyone up ahead.
Or at least that was the gist I got from Peter Kostis' comments when it became obvious that DJ was in serious struggle-mode.
Which, mind you, doesn't mean a whole lot since it takes all of these guys 5+ hours to play 18 holes on a regular tour event. It's just that they have an opportunity to blame the amateurs playing alongside them this particular weekend for the slow pace.
I'm guessing that played a part in his frustration, but would still be very surprised if he didn't at least attempt to congratulate his playing partner for winning.