Sydney FC has signed 18-year-old National Youth League defender Sam Gallagher for the rest of the 2009/10 Hyundai A-League season as an injury replacement for Matthew Jurman.

Gallagher started the year with Manly United in the New South Wales Premier League before joining the Sky Blues Youth League squad.

After immediately impressing with a number of standout performances, Gallagher began training with the A-League squad this week.

"Sam has been impressive since beginning training with the A-League squad. He works hard and that is very important at Sydney FC," coach Vitezslav Lavicka said.

"He has done well in the youth team since coming in. We know if he gets the chance to play in the A-League that he will do well. He is learning every session."

Gallagher recently represented Australia at the 2009 FIFA U20 World Cup in Egypt.