McIlroy, who had dropped out of contention at the US Open, delighted organisers with his decision to contest the Scottish Open last month.
He went on to set a new Royal Aberdeen course record of 64 on the opening day but handed back the seven shots on day two before finishing his first Scottish Open in four years with scores of 68 and 67 for a share of 14th place on seven under par.
As Bannon was photographed alongside McIlroy with the US PGA Championship trophy on Sunday night, he reflected upon the decision to play in Scotland. "Rory and I went back to his roots the week before Royal Aberdeen as we went back to the practice ground and the club at Bangor," said Bannon, who has coached McIlroy since the age of seven.
"We stayed there all week except for two days at Royal County Down and that got the ball rolling. We tried to keep his ball flight down and played a lot of links golf, then went to Scotland and played more links golf.
"Playing the Scottish Open was pivotal as it is the best preparation I've seen Rory undertake heading into the Open; it just gave him a massive boost in confidence. It's funny too because, when Rory gets playing well, he kind of knows he's going to win these tournaments.
"The greatest thing about winning a PGA is that he didn't give this one away, and you have to say, 'How good was he today?"
While Scotland waits for a first major championship winner since Paul Lawrie won the 1999 Open, Irish players have now won nine of the past 30 majors, following the triple success of Padraig Harrington in 2007 and 2008, four for McIlroy and one each for Graeme McDowell and Darren Clarke.
Ahead of the Masters next April, Bannon believes there is nothing stopping his 25-year old charge becoming on the sixth player in the history of the game to win a coveted grand slam.
"Augusta really suits Rory and, this year, if he had putted well, he would have been right up there," he said.
"One of these days I think he is going to win the Masters. It was great he won the Open, as the Open for us … I watched golf in the '60s, '70s and '80s; you didn't see much American golf on the TV and I really looked forward to the Open as it was always being played so close to us.
"On the green back home, when I was training him, Rory would say he was holding a putt to win the Open, so, for me and everyone one around him, to win the Open was massive."