The promising centre-back pair have agreed deals to remain at Bluetongue Stadium after becoming important first-team regulars
Sainsbury and Anderson's deals were set to expire at the end of the season but both youngsters, who broke through as part of the Mariners' championship-winning campaign last term, have decided to stay in Gosford despite interest from elsewhere.
Anderson has signed on until the end of 2014-15, while Sainsbury has a contract for a further season on top of that.
Central Coast have claimed that both other A-League outfits plus clubs from abroad approached the defensive duo but 21-year-old Sainsbury and 22-year-old Anderson explained they were never truly tempted to leave just yet.
"I have a burning desire to go overseas," said Sainsbury, who has yet to miss a minute in 2013-14 and made 26 appearances as Central Coast lifted the championship trophy last season.
"But I don't want to go over there with nothing behind me - I want to arrive at a club and be very well respected for what I have achieved in Australia."
Anderson was also regularly involved with the Mariners last season, although of his 23 appearances, 12 were off the bench, but the Queenslander has started all but one match this term.
"I am over the moon to have signed an extension with the club," Anderson said.
New Central Coast head coach Phil Moss believes Anderson and Sainsbury could become the Mariners' leading central defensive pairing, despite their youth and Dutchman Marcel Seip providing competition.
"Trent and Zac have become very important players for us," Moss said.
"We're delighted they have committed to the club, because they are two players who show great leadership and understand what it takes to achieve at the Hyundai A-League level, and in the AFC Champions League.
"They are physically strong players with great attitudes and fit our culture perfectly."