Incorporating some type of cardio vascular exercise into your weight training programs is a smart thing to do. A strong cardiovascular system will allow you to perform better in all aspects of your physical activities including weight training. However, you should never try and serve two masters. This may severely sabotage your muscle building efforts.
If your priority is to build lean muscle mass, you should have an all hands on deck mentality for this activity. Your entire program and eating patterns should be targeting this goal. Cardio will have a part to play; it just won't have the leading role.
For example, if your goal is to bring up your skinny legs and add an additional 10 pounds of muscle to your frame, you're going to have to stay away from those long jogging sessions. You can't expect to have great leg workouts (which are needed to grow) if they are constantly tired from running. To build quality muscle mass, your body has to be well rested for each workout session.
My suggestion is stay away from those super long (or high intense) cardio sessions on your workout days. If you want to perform your cardio sessions after your workouts, fine. Just don't try and set any records with your cardio prior to performing your workouts. Remember, hard and heavy workouts first and cardio exercise after (see this article for more info)
This goes for all activity including sports. If you play hockey two days a week, I suggest keeping both activities separate. That is, hockey days are specifically for hockey and workout days are strictly for workouts. This will help keep your muscles fresh and ready for both activities.
Remember, stick to your priority!!