Sydney Swans co-captain Kieren Jack is the first to admit that younger brother Brandon has exceeded all expectations so far in his debut season with the club.

Brandon, who arrived at the Swans via pick 58 in the AFL Rookie Draft at the end of last year, made his senior  debut in round 11 against Adelaide, and has since played two more games including last weekend’s breakout, four-goal performance against Melbourne at the MCG.

Speaking ahead of this weekend’s Sydney Derby at the SCG, Kieren said Brandon’s meteoric rise this season has come very much as a surprise.

“In all honesty, I didn’t (think he would play this year), he was a very skinny, raw kid,” Kieren said.

“I’ve said since November his improvement has been exceptional and he surprised me. I knew he had talent but he has certainly surprised me in the way he’s come in and been able to adapt and learn the game plan and structure so quickly.

“Athletically he was sound but he improved over probably two or three months in his fitness ability and his skills and he’s just come along way and I now just have a big smile on my face when I run out alongside him.”

Kieren said the secret to Brandon’s rapid success this season was likely to be his little brother’s intelligence and attention to detail.

The co-captain said Brandon, who achieved an impressive 98.4 in last year’s HSC results and aspires to study law, has the ability to listen to, and comprehend, advice from the Swans’ coaches and senior players.

“I’ve been rapt with his development and the way he’s improved,” Kieren said.

“We watch a fair bit of footy together and I think one of the things he does do really well is that he talks to Henry Playfair, who is our forwards coach, he talks to Jude Bolton, who is his mentor, and he’s really absorbing a lot of information at the moment.

“He’s a smart kid, but he really listens and he does what the coaches want from him and on the weekend he was super.”

While the younger Jack brother says he wants to follow in his brother’s footsteps, Kieren said it was unlikely Brandon would play the same type of role on field for the Swans.

Kieren said Brandon’s height, speed and athleticism could see his brother develop into an outside runner, similar to Lewis Jetta.

“He’s a bit taller than me and he could probably play that half forward/wing role,” Kieren said.

“He’s probably watched a few too many of my games where it’s in and under, but he’s got some strength there that he can run and leap.

“He can be similar in the way to Lewis Jetta or Gary Rohan and can be a similar type of player to that because he does have that electrifying speed that he can use on the outside which is pretty important in today’s game.”

With a number of injured Swans still yet to return to the senior side, Kieren said he believed Brandon has what it takes to play an important role for the Swans as September draws closer.

“He’s certainly got the level head for it; I don’t think he’s getting carried away,” he said.

“We do have some injuries at the moment but he’s earned his spot to come in and he’s certainly making the most of it at the moment.

“He got himself in some really good spots and worked hard on the weekend and he came out with four goals, so while that might not happen every week, he knows that if he works hard he’s going to give himself every chance.”