In an interview given immediately after winning his first major title, Dufner admitted that the victory is yet to sink in, after overturning a two-shot deficit in an assured display.
He said: "It was a tough day, a long day and it hasn't hit me yet, I can't believe it is happening to me.
"To come back from a couple of years ago, when I lost to Keegan Bradley in the playoff, feels really, really good. I'm privileged to play in these tournaments and it is a great feeling to win one.
"I decided I was going to be confident, put my best foot forward, be aggressive and try to win this thing, not be scared or too soft. I'm happy to get the job done and it is a big step in my career."
The 36-year-old finished on 10-under-par after 72 holes, setting a record at Oak Hill for the lowest score hit in a major tournament at the famous course.