Tape,
The one playerout of focus is due to depth of field which is how much of the image from close to through far from the photographer is in focus. Depth of field in focus is determined primarily by lens focal length, aperture setting, and distance of the camera from the subjects. This is a pretty handy calculator that will show the depth of field in critical focus for various lens/distance/aperture scenarios.
https://www.pointsinfocus.com/tools/depth-of-field-and-equivalent-lens-calculator/
Select your camera and lens and the calculator will let you see what the depth of field will be in various situations. Most Canon models also have a depth of field preview button that will step the aperture down so that you can see what is in focus before capturing the shot but this is of limited benefit because you will end up with an often dark viewfinder view and with not enough detail to truly tell what is in focus. Liveview can also show depth of field but it isn't very useful for shooting action.
Many sports photos will have shallow depth of field out of necessity and not just by design. Those photos in my post were captured in a very poorly lit stadium so I was using a telephoto prime lens with the aperture wide open to let in as much light as possible which results in a very shallow depth of field.
When the subjects aren't moving, you can use a slow shutter speed and close the aperture down for greater depth of field but with sports action, slower shutter speed generally isn't an option. If you need more depth of field without motion blur from player action, your only option is to keep the shutter speed the same while closing down the aperture which will force the ISO higher resulting in more noise and loss of detail.
Rodger
EOS 1DX M3, 1DX M2, 1DX, 5DS R, M6 Mark II, 1D M2, EOS 650 (film), many lenses, XF400 video
