The club were hoping to conduct a medical on Tavares, who will join fellow Sky Blues exile and cousin Jacques Faty in Gosford next season, but are still awaiting confirmation of his release from the final year of his Sydney FC contract.
However, the Mariners remain confident that once the red tape is cut the deal will progress unhindered and the Senegalese midfielder will sign a one-year deal for the 2016-2017 season.
Tavares, 33, is part of Sydney FC's AFC Asian Cup squad but dropped down the A-League pecking order under coach Graham Arnold and was not in his plans for next season.
He racked up 22 appearances this season but failed to feature for the past three games and his exit from Moore Park was anticipated.
With his combative qualities and experience, Tavares is viewed by Walmsley as a torchbearer for a youthful squad which was brutally exposed this season in slumping to the wooden spoon.