Hi guys, I've committed to photographing a few upcoming lacrosse games. Since I never shoot sports, I don't own any "sports" lenses and would have to rent one for the events. I was thinking of getting a 70-200 2.8 IS but now I have the opportunity to borrow a 135 f/2. Have any of you photographed any football games or any other field sports with the 135 f/2? Is it quick enough? Will I have to run around the field like a mad man or it is manageable and I can expect to be able to get good shots? I appreciate your input.