One of 26 players who had to complete the round on Sunday morning at Kiawah Island, the 32-year-old Australian bogeyed both the 11th and 16th on the way to a level-par 70.
He covered the more difficult back nine in two-over 38 to finish at three-under 213, four strokes behind pacesetting Northern Irishman Rory McIlroy.
"I played well again, just a couple errors on the par-fives," Scott told reporters after a round that included four birdies in a sizzling outward nine.
"I was in good position, but a couple of poor shots and I ended up making six from a position I should be making four.
"It's put me a little bit behind the eight-ball starting this afternoon. I'm going to have to play very well and make some putts."
Scott, who squandered a four-shot lead with four holes to play in last month's British Open at Royal Lytham, had steeled himself for a gruelling last day at Kiawah where he will end up playing 27 holes.
"This afternoon is the last round of a major in contention," said the world number seven who has yet to win his first major title. "To have a good round and try and win requires mental toughness.
"You know, the 27 is not a big deal, but this afternoon as it comes down to the back nine, especially at this golf course, is going to require everyone's skill to be at their best."
Asked if he had changed his playing strategy because of the relatively calm early conditions on Saturday, Scott replied: "I just played the way I thought the course needed to be played.
"There wasn't much change, maybe just off the 13th tee where I wasn't planning on hitting an iron off that tee this week, and today I did. I hit a poor one, but I made four.
"It was just a couple of errors on the par-fives ... and I didn't make the six-foot putts that I've been making all week. I've got to make them this afternoon."
- Sports & Recreation