"Hopefully the old spark lights up again as I am just trying to get something going.
"I have just struggled with that this year and I think this will help."
While the pair had plenty of success, by the end of their stint in 2014 frustrations were clearly evident as their differing personalities clashed.
Williams, a Kiwi who was also on the bag for 13 of Tiger Woods' 14 major championship triumphs, is widely known as the best in the business and has a hard competitive edge.
Scott, while also competitive, is calmer in nature and when combined with the also calm Kerr was unable to fire.
"I spent four years playing with him (Williams) at a really high level and enjoying that energy," Scott added.
"It is tough to maintain that.
"There is a lot of strain and pressure doing that and there has been a bit of a letdown on my side in the last six months from that.
"This is the thing to get me back up there."
It was a reunion that may not have happened, given Williams was enjoying his retirement, racing cars and coaching rugby.
But he declared himself ready to be the help Scott needs for this week and also at the British Open, the WGC Bridgestone and the US PGA Championship in their limited reunion.
"Absolutely, I wouldn't be here otherwise," said 51-year-old Williams.
"I've absolutely 100 per cent enjoyed not being a caddie - just having a normal routine. When you've been out here as long as I have, you don't miss that.
"But look, if you had an option to come back and work a few tournaments, it's a pretty good four to work.
"This is a fantastic place [and] St Andrews (for the British Open) - there's no better place than that in golf."
-AAP