Coach Tony Popovic has vowed his Western Sydney Wanderers won't take their foot off the accelerator with the rampant A-League rookies now in the box seat to claim the Premier's Plate in their first season.The Wanderers surged to short-priced favouritism to finish the regular season on top after taking the ladder top spot by two points from longtime frontrunners Central Coast Mariners in an epic 1-0 away win before 18,721 fans at rain-soaked Bluetongue Stadium on Saturday night.With just four rounds to go Popovic's men (15 wins, 2 draws, 6 losses: 47 points) have a friendlier draw than the Mariners (13W, 6D, 4L: 45 points), who must also continue to do double duty with an Asian Champions League commitment away in Japan between their next two matches.Cross-city rivals Sydney FC could do the Wanderers a huge favour - ahead of the eagerly-awaited derby clash in three weeks - by knocking over the Mariners at Allianz Stadium on Saturday, while Western Sydney are at home to last-placed Wellington Phoenix the next day."Every week you ask me the same thing: 'will they (the players) get complacent?'" said Popovic."Eight wins in a row shows they're not getting complacent and they certainly won't be next week."That doesn't guarantee a result against Wellington but I can guarantee you they'll be well prepared for that game."Buoyed by the raucous support from more than 6000 Wanderers faithful who drowned out the home crowd, the visitors triumphed against the run of play through a well-taken late winner from substitute Labinot Haliti.Not only was it the Mariners' first home defeat all season, it meant the Wanderers have now beaten every team in the league."On reflection at the end of the year we'll look back at all that but now's not the time to reflect on milestones," Popovic insisted."We get back, make sure we recover and prepare for Wellington."Mariners boss Graham Arnold, knocked off top spot for the first time in 14 straight weeks, is certainly not giving up on back-to-back premierships.But he said his team must rediscover the scoring touch that dismantled Melbourne Victory 6-2 last week."There's a lot of twists and turns to go. There's four tough games for everyone," he said."If you don't score when you're dominating you're vulnerable."It's a hard lesson to learn but it's a lesson we've got to learn and we've got to move forward - simple."Perhaps another lesson the Mariners must learn is how to take penalties after squandering their third spot-kick in as many matches.Daniel McBreen failed to score from the penalty spot last week against Victory before Nick Montgomery suffered the same fate in the Mariners' Asian Champions League game against Suwon Bluewings on Wednesday.An unlikely penalty-taker in goalkeeper Mathew Ryan stepped up to the mark on Saturday night and had the chance to put the hosts in front.Instead his fellow gloveman Ante Covic saved his strike and that disappointment was compounded later when a McBreen snap shot from close range ricocheted off the cross bar."If you've got goal scorers out there, they should be the ones that want to take it," Arnold said."It's probably gotten to the stage where you've got to designate someone specifically now and he has to take that responsibility."Even if he misses he backs up and does the next one."