Sometimes, in spite of having an ideal subject, you still can't get the photo you want. Your subject might be front and center in the scene; but due to poor lighting, the shutter speed is so slow that everything is a blur.
The fix? Find your camera's ISO control and increase it a couple of steps. ISO measures your camera's sensitivity to light; shooting at ISO 400 instead of ISO 100, for example, means that you can possibly catch a photo at 1/60 second instead of 1/15 second. That's the difference between being able to read the letters on a player's jersey and ending up with merely a blur.
The downside to increasing the ISO is that you'll have more digital noise in the photo, but if increasing the setting makes the difference in getting a sharp photo, it's probably worth it. This wolf never stopped moving, for example, so a high ISO froze the action at the cost of making a grainy photo. Like white balance and manual focus, ISO is a setting that you should remember to change back after your action-photo shoot.