Challenge games do not focus the mind as much as when three ponts are at stake Kris Commons is getting used to the idea of switching between competitive games and friendlies since the league started. Since beating Hibs in the SPL opener a almost a fortnight ago, Celtic have played four challenge games - the most recent against Swansea in Wales on Wednesday night. Now Commons is ready to get back into the SPL mindset. He said: "You have to flick a switch in your brain to think that you are back in competitive football now. It is a must-win game and three points are required. So you do everything you have to do to be prepared for that. We know they will be fired up and we know it's going to be a tough game. But, like every game we play in, we want to win and if we play to our potential we will get the three points.'' Last season Celtic beat the Dons five times out of five but manager Neil Lennon is expecting Craig Brown's side to bounce back from last week's loss at St Mirren. He said: "I expect a response from them. By all accounts they were disappointed with the performance against St Mirren and, as with all teams, they will raise their game against us. It is a new season and Craig and Archie (Knox) will have had time to work with the players last week. They will be well organised and will have something up their sleeve for us so it will be a tough game for us and we will have to be at our best. I think the players will be looking forward to a game with a competitive edge. But we have needed the challenge games to work on a few things and so they have been worthwhile.'' Meanwhile, Commons is hoping Celtic skipper Scott Brown, who will serve the second of his two-match ban this weekend, ends any uncertainty about his future by signing a new contract. The former Derby and Nottingham Forest player said: "It is vital. Scott is our captain, he is our leader and leads by example. He is an international player, he has plenty of qualities, and when you need him in the big games he always shows up. I'm sure he will get his future sorted sooner rather than later.''