"I just knew that if he got up the inside that would be it. I was very conscious of protecting the inside," Power said.
"He was very fast at the end there.
"What a day - I am spent. It was a seriously dramatic day but a lot of fun."
Dixon had mixed feelings at the end.
"I think maybe we trimmed it too much at the end. It seemed that some of the other cars could run a bit closer," the New Zealander said.
"Fifth and sixth is something to take home, something positive.
"Championship - we moved up a spot but the 2 car spread the championship a bit.
"We know St Louis is going to be a real tough one as we saw in pre-season testing - it has such long straights there. It will be get what you can at St Louis.
"Hopefully we can take something away from there and then finishing strong at Watkins Glen and Sonoma."
Newgarden holds an 18-point lead over Dixon but Helio Castroneves, Simon Pagenaud and Power are all within striking distance, setting up a spectacular finish to the season.