Nathan Merritt's sister says the South Sydney great's condition is "improving slightly", with the 40-year-old remaining in a Sydney hospital. 

Merritt was rushed to the city's Royal Prince Alfred Hospital on Friday and placed on life support, after being found unresponsive at his aunt's residence.

The former Rabbitoh is believed to have had an adverse reaction to prescribed painkillers.

Merritt's sister, Teanne, posted on Facebook on Tuesday afternoon to say the family had received somewhat positive news on the winger's condition.

"We have been advised that Nathan is improving slightly but has a long road to recovery," Teanne Merritt posted.

"We thank everyone, family and friends that have come up to visit Nathan and all the well wishes and kind words from all."

A cult hero at the Rabbitohs, Merritt scored 154 tries in 237 NRL games and remains equal-12th on the league's all-time try-scoring list.

He retired from the NRL in 2014, but played in the Koori Knockout on the NSW Central Coast this month.

AAP