KENYAN-BORN Sydney Swans key defender Aliir Aliir has been picked to make his AFL debut against the Brisbane Lions at the Gabba on Sunday.

Aliir will replace veteran Ted Richards who fractured his cheekbone in the Swans' 39-point win over West Coast last week.

Who is Aliir Aliir? Five fast facts

The 21-year-old was born in a refugee camp in Kenya to Sudanese parents before his family fled war-torn Africa when he was seven years of age to settle in Australia, firstly in Brisbane, and later in Perth.

It was a season spent playing for East Fremantle in the WAFL where he impressed the Swans, who took him at pick 44 of the 2013 NAB AFL Draft.

Coach John Longmire said the athletic backman has benefitted greatly from playing on the likes of Lance Franklin and Kurt Tippett during match simulation and has dramatically improved his game since the end of last year. 

"That’s the benefit for our young key defenders is the ability to be able to train on quality key forwards on a regular basis," Longmire said.

"There's no better way of learning, we can show vision as much as we like but there's no better way (to learn) than playing on the best.

"Particularly over pre-season and games to this point so far he's been terrific winning his one-on-ones and he's a very good kick and a great athlete. 

"He's played on a couple of listed AFL players at reserves level and done OK, and certainly at training he's been good at that as well.

"It's really exciting for him, he's put together a great body of work in the reserves, he's played a good 5-6 weeks of absolute quality football now and deserves his opportunity."

Longmire said he kept news of the club's latest debutant quiet until the team's pre-training meeting on Wednesday, and he got the reaction he expected from the playing group.

"He didn't know actually, I announced it and his was probably the best grin I've ever seen," Longmire said.

"He's had a few challenges along the journey, there's no doubt about that, but he's making the most of his opportunities now and it's terrific to see."

While Richards will miss the clash with the Lions, Longmire was confident that fellow defender Jeremy Laidler would be cleared to play after he missed most of last week's win over the Eagles after copping a head knock early in the game.

In other news, speedy midfielder Gary Rohan will play in the NEAFL after coming off the long-term injury list.

The 24-year-old's hamstring issues forced the club to give him an extended time away from playing to ensure he returned to full fitness, and Rohan looks to have himself in great shape after training at full pace with the Swans' main group for the past month.