Adelaide United have punted on a Kenyan teenager to fill a void in what coach John Kosmina terms a dangerous time of the A-League season.Awer Mabil, a 17-year-old who came to Australia in 2006, has been summoned for Friday night's encounter against Perth Glory as injuries begin to mount on the second-placed Reds.Mabil will come from the bench in his A-League debut at Hindmarsh Stadium to help cover the losses of Portuguese winger Fabio Ferreira and Argentine attacker Marcelo Carrusca, both sidelined by groin injuries."Awer has earned his chance from his performances in the youth team and he gives us a lot of speed and an X-factor," Kosmina told reporters on Thursday."The youth team is there for occasions like this where you have got a number of different injuries. If you look at him and Fabio, it's almost like for like. They're both quick - they're both natural right wide players."Adelaide hold second spot, four points shy of league leaders Central Coast and three points ahead of third-placed Melbourne Victory.Kosmina said along with some injuries, the Reds also had three players carrying four yellow cards - five yellows is punished with an automatic one-match ban."It is going to get harder," Kosmina said."The other teams have got better and we have still played in patches and played well."It is a dangerous time."You do get your niggles, and we have got three players on four yellows as well, so there will be a turnaround of starting line-up in the next month, I would imagine."Kosmina, who refused to talk about his coaching contract expiring at season's end, was wary of Perth and their striker Shane Smeltz, who scored twice in a 2-2 draw with Sydney FC last start."They are tough mentally and they are tough physically," Kosmina said of the Glory."We have got to be aware of Smeltzy ... he has learnt to think his way through the game, which he wasn't doing when he was a lot younger."So he's smart, he makes good runs, he gets into good areas at the right time and he's an exceptional finisher."