Melbourne Victory coach Ange Postecoglou has warned squad changes in the January transfer window are likely if the A-League club's leaky defence cannot be plugged in coming matches.Despite an unbeaten run of three games, the Victory are allowing untimely goals with frightening regularity.Only Sydney FC have conceded more goals this season - in large part due to their 7-2 smashing by Central Coast a few weeks ago.Postecoglou says he will give his existing personnel the chance to sort out their problems.But if they don't, he says the January transfer window could be an opportunity to bring in players who can."Maybe," Postecoglou said when asked if he would look outside the club to strengthen his defence."If we start looking to the transfer window from now, we'll miss about 10 games which could define our season."It's more about the players we've got at the moment and improving our performances in those areas."We need to stop conceding goals, and the goals we're conceding aren't the greatest."Defensively it's an area we need to strengthen, no doubt about that."But Postecoglou is thrilled with his side's creativity going forward, with the Victory's 12 goals in seven games making them the league's second top-scorers.The Victory will take on Western Sydney Wanderers at Parramatta Stadium on Saturday night.