Newcastle have yet to record a clean sheet this A-League season and midfielder Ruben Zadkovich says the Jets will be focussed on tightening their leaky defence when they host Wellington on Sunday.While Newcastle are equal with ladder leaders the Central Coast in scoring the most goals so far this season with 11, they have conceded almost as much with 10 goals scored against them.Coach Gary van Egmond has continually emphasised the need for his charges to keep a clean sheet and Zadkovich feels it's time to head his advice."I think he's right," Zadkovich said."We can't go a whole season conceding goals the way we are and expect to win anything."So if we really want to be there at the top we really need to tighten up at the back."Playing Wellington at home is probably a good game to try to get a clean sheet and if we can do that we've proven early on that we can score goals so it's all about trying to keep our structure."With former Sheffield United and Crystal palace striker Paul Ifill up front for the Phoenix, the Jets defence will have a lot of work to do.The Barbados international has so far scored 29 goals in the A-League since joining Wellington in 2009 and while Zadkovich knows he'll need to nullify his impact he says he enjoys facing tough players."It's hard to single out any player but for me personally I think Paul Ifill is a great player. He's hard to mark and play against," he said."So I'll have to try to keep him quiet."But no player gets under my skin ... I love someone who fights on the pitch and has a real good crack, that's what I love and that's what I play football for."The Jets were totally dominated by Western Sydney Wanderers last weekend, yet walked away with all three points.They now sit third on the table, a point off top spot, and have a dangerous striker of their own in Liverpool legend Emile Heskey.Zadkovich feels if they can just control play more regularly they'll be on their way."I think we've played well in patches in games," he said."I think in 15 minute spells in some of those performances we've been outstanding."So if we can just lengthen those periods of when we're controlling the game then we'll get even more wins."So it's a good thing that we're not playing our best and wining games."The Phoenix meanwhile have slumped badly with three successive losses and sit at the bottom of the ladder.They will also have to deal with fatigue after several players were involved in New Zealand's 1-1 friendly draw with China midweek.