Central Coast has signed former Perth Glory and Wellington Phoenix defender Brent Griffiths on a one-year deal.
Griffiths, 22, knows the club well after spending two months training with the Mariners last season before his move to Phoenix, while elder brother Rostyn also played for the club before heading to China.
"Brent gives us A-League experience having played with both Perth Glory and Wellington Phoenix," Mariners coach Graham Arnold said.
"He offers us further depth in the centre of defence, where we also have Patrick Zwaanswijk, Zac Anderson and Trent Sainsbury.
"Brent gives us good cover at left stopper and can adapt to a number of other roles on the pitch should we need him to.
"We were interested in keeping Brent at the Mariners last season, understand his character and know he will fit into our club culture."
Griffiths, who has been turning out for Heidelberg United in the Victorian Premier League, said he was looking forward to learning from the likes of Arnold and fellow defender Zwaanswijk.
"It was an easy decision to come to the Mariners - they are the best club in the A-League as far as I'm concerned," Griffiths said.
"The guys are good lads, the coaches are great and the facilities are very good, too."
Goalkeeper Mat Ryan, defender Pedj Bojic and midfielder Oliver Bozanic look to have played their last games for Central Coast Mariners as the A-League champion faces a raft of departures.