Central Coast Mariners have reached agreement with Young Socceroos defender Trent Sainsbury to extend his deal with the club for a further two A-League seasons.

The 20-year-old is rated as one of the competition’s best young defenders, with the Mariners fending off approaches from several rival clubs.

Sainsbury on Tuesday revealed some of the key reasons behind his decision to stay with the league leaders until at least the end of the 2013/14 campaign.

“It’s a good family-orientated club, which suits me, and I like that it’s a very chilled out lifestyle here on the Coast,” Sainsbury said.

“Arnie (coach Graham Arnold) was a big part of me staying here.

“He’s a very professional coach, and I guess you don’t know what you’ve got until it’s gone so it was important for me not to go to another club and basically have to start from scratch.”

The Mariners have also announced the promotion of three National Young League (NYL) squad members to the club’s 2012/13 A-League roster.

Attacker Mitchell Duke, utility James Oates and midfielder Anthony Caceres have been rewarded for their stellar form in the 2011/12 NYL.

Duke has secured a two-year deal, while Oates and Caceres have been signed to initial one-season contracts.

The trio have also been added to the Mariners’ 2012 Asian Champions League (ACL) squad.

Mariners’ mastermind Arnold praised the club’s promotion of Duke, Oates and Caceres, and the retention of Sainsbury.

“This shows that we want to give our youth a go,” Arnold said.

“The ones who come into our system early will get a chance – to find other players they have to be a very special talent otherwise we will promote our youth.”

Central Coast begin their ACL group stage on Wednesday March 7 away to Tianjin Teda in China.

They then play two Group G games at home against Seongnam Ilhwa Chunma (Korea Republic) and Nagoya Grampus (Japan).