I cover the Fort Myers Miracle, farm team of the Twins, at the Twins spring training stadium which is lit to MLB standards. At night I typically shoot 1/1000 sec, f/4, ISO6400. You are going to find that you will be using the long end of the 100-400 which is f/5.6, so you are looking at 1/500 or ISO 12,800. Shooting from the 3rd base side dugout with a full frame camera it takes a 300mm lens for a tight shot at home and 400mm for 1st at Hammond Stadium. The dugouts and stands at Hammond are much closer to the baselines than the MLB stadiums that I have been to in the Northeast. You may well find that 400mm does not put you close enough to the action to make a rental worthwhile.