It depends. For sideline passes, you only need 200mm on a 1.6x crop body = 320 and for some shots, that's still too close. If you are in the stands, get the 300 f/4L, because that'll be 480mm. 400 lens for football and soccer is way too long on a crop, unless you are WAY back in the stands. If you have a sideline pass, effective focal length of 300mm is the farthest you want to shoot. I use a 300mm lens on FF for sideline passes, and I still have to have a 70-200 lens on another camera for closer action.