There's a good website for people with type 1 diabetes who want to do sports - many sports covered - www.runsweet.com
Your diabetes team should be able to give you appropraite advice, depending on the insulin regime you use, but basically, you can reduce insulin before exercising. Also, timing exercise to a few hours after most recent fast acting insulin, can help. You may also need to reduce long and short acting insulin in the hours after exercise. Hope you get back to football very soon - the season's started!