Various apertures will have various applications, often times, f8 is ideal - even in outdoor sports (plenty of bright sun light to achieve a 1/500th shutter even at f8). The aperture you want to use will depend on the angle and range of the shot - distance of subject, distance between subject and background, etc etc. F8 has plenty of uses, one such use is to squeeze light through the lens sweet spot, eliminating many lens problems that present themselves shooting wide open. Sometimes an f2.8-f5.6 aperture is ideal, sometimes f8, for more close-up telephoto photography in bright light sports, f8 quite often is more appropriate. The popping action of the softer bokeh won't make a difference if its only the baseball players shins that are in focus as he slides home.