Friday September 7, 4:28 PM AAP Manly hooker Michael Monaghan says the Sea Eagles must be prepared to start winning ugly again if they are to ignite their NRL premiership campaign with victory over South Sydney in Saturday night's qualifying final at Brookvale Oval. The Sea Eagles have built their season around crunching defence which choked the life out of their early season contests, but a late slump has seen their line concede a total of 60 points in the second halves of their last three games. Monaghan says while Manly could afford to switch off during the regular season, they know any lapses against the determined Rabbitohs will almost certainly end in another finals defeat. "Semi-finals are all about the full 80 minutes," he said. "Obviously during the regular season you can get away with not finishing games off properly but you get found out in semi-finals. "Before that stretch (the final three games) we had been the best in the comp in the second half so I guess we need to get back to that and really start getting some sting back in our defence. "The most important thing is to come away with a win. Whether it's ugly or whether it's pretty you've just got to make sure you get the win and that's all we want." Manly's recent losses have been blamed on a run of injuries to key players - although most were rested to overcome minor niggles ahead of the finals series. But the Sea Eagles will be without two key forwards on Saturday with Test prop Brent Kite (adductor) and Glenn Hall (shoulder) ruled out with injury. Their absence has forced Adam Cuthbertson into the starting line-up, alongside Jason King who has played just two games since a serious knee injury. Monaghan knows the Rabbitohs - led by arguably the world's best prop in Kiwi Roy Asotasi - will look to dominate Manly's depleted pack. "They rely on a lot of big guys who just go forward and they tend to get their points off the back of those blokes," said Monaghan. "Guys like Asotasi and their front-rowers, we have to try to contain them. "Obviously with Kitey missing and Glenn Hall it might be an area they think they can expose us but we'll just see. "(Kite's) a Test prop so obviously he is one of the top players in the competition and, while we will miss him, we certainly have the blokes there that can fill in. "What has got us this far this year are the blokes who have come in and filled positions have always done a good job, so I guess the acid test will be on those guys this weekend." Victory for Manly would guarantee the Sea Eagles a week off and move them to within one win of a grand final berth. Monaghan, who leaves Manly at the end of the year to join Warrington in England, knows this is the best chance of his career to win a coveted premiership. "In your career you don't get too many genuine opportunities to win the competition and it's certainly my first time where I've really thought we are a genuine chance," Monaghan said. "You certainly have to take those opportunities when you get them."