BY ANY measure, Josh Kennedy's decision to leave Hawthorn and join the Sydney Swans has been an extraordinary success.

But, on the eve of his 100th AFL game, Kennedy has conceded he still had doubts about his ability to make it as a professional footballer when he made his career-defining move.

In three years as a Swan, Kennedy has finished third, equal-second and first in the club best and fairest, adding a premiership and an All Australian jumper to his Bob Skilton Medal in 2012.

He also hasn't missed a game in red and white, set to play his 87th consecutive match against Melbourne at the MCG on Sunday.

Such levels of success make it seem difficult to comprehend now, but only 13 appearances in three years as a Hawk left the 25-year-old questioning his ability to cut it at the highest level.

"I didn't have too many expectations coming here three-and-a-half years ago," Kennedy told reporters on Friday.

"At the end of the day it was an opportunity to see whether or not I was good enough.

"The worst-case scenario was it'd be a good experience to live in a different city away from home.

"The greatest thing for me was just to get a game and see whether or not I was up to the standard."

At the end of 2009, the Hawks were only prepared to offer Kennedy a one-year extension, while the Swans had tabled a three-year deal.

For a man who is still working his way through a commerce degree, the decision was, in his words, a "no-brainer".

Kennedy, who penned a new four-year deal earlier this year, still feels indebted to the Swans.

"That was the bottom line in the decision," he said.

"Not only were they telling me that they were going to play me, but a three-year contract from only playing 13 games (with Hawthorn) added fuel to their argument."

Despite his success, and the profile and respect he now he enjoys across the AFL, Kennedy can still be extremely self-deprecating.

He puts his durability down to "good management, the fitness staff here and the fact I'm not quick enough to do any soft tissue injuries".

And he credits John Longmire with giving him the confidence he needed to make it in the competition.

"Huge. Huge influence," he said when asked about his coach.

"He was the midfield coach when I first came up and then obviously head coach and he just constantly instilled confidence into me and getting back to the basics and knowing what works for me."

Similarly, Longmire has enormous admiration for one of his star pupils.

"His consistency has been at an incredible level and his ability to play on a consistent basis in big games has been remarkable," Longmire said.

"He's as hard and clean a contested ball player as you'll see and he's also a massive body and can take an overhead mark when he goes forward.

"We've had the retirements of Brett Kirk and the like, and to have a player like him come into our midfield has been really important.

"He's now in our leadership group and he's making a real mark on this footy club."

James Dampney is a reporter for AFL Media. Follow him on Twitter @AFL_JD