Once you draft your team and join a league, by default all of your lines will be set with the first center, first left wing, and first right wing you drafted. All of your pairs will be set with the first two defensemen you drafted. It is STRONGLY recommended that you set your lines and pairs differently than this. You want to make sure that when a new line goes out on the ice, it contains three fresh players. The same is true for your pairs. If your players get too much ice time, they will begin to fatigue. Even the toughest players rarely get over 30 minutes of ice time in a game. Try to configure your lines and pairs accordingly so that players get appropriate rest time between shifts. Needless to say, fatigued players will not perform to the best of their abilities. The more fatigued they are, the worse they'll play. Highly fatigued players are also more likely to get injured.