FORMER Socceroo and English Premier League defender Hayden Foxe today signed a six week contract with Sydney FC as an injury-crisis grips the league leaders.

Foxe passed a series of fitness and medical tests this morning and with his signing approved by Football Federation Australia (FFA) this afternoon, he will play for the Sky Blues against Perth on Sunday.

The signing comes after Sebastian Ryall was ruled out for six weeks after straining the medial ligaments in his left knee at training yesterday, leaving Sydney's thin defensive stocks badly stretched.

Sydney hope Foxe will be able to bolster the backline providing he can stay injury-free after being plagued by problems during his time at Perth Glory.

"Hayden is an absolute professional," assistant coach Tony Popovic said. "He has represented the Socceroos and played in the English Premier League so he brings a wealth of knowledge to the group.

"We have had a few injuries in the last few weeks, especially in our defensive ranks, so Hayden provides us with another body and a lot of experience."

Foxe represented Australia at the 1996 Atlanta and 2000 Sydney Olympic Games and played for West Ham, Portsmouth and Leeds United in the English Premier League, before joining Perth Glory for two seasons in 2007.