Thanks for the photos. They are a little small but I feel the night shot is showing camera motion from too slow a shutter speed or too long a focal length to be hand-held for a nighttime exposure. You will need to boost your ISO to a higher level to make faster shutter speeds possible. The daytime shot doesn't show as much camera movement in the tiny image but probably is quite apparent in a larger size. Again, if you are using the extreme telephoto setting, handholding will be more difficult. Also when shooting movement, if you had focussed when the runner was at another distance but took the picture farther down the field, the focus would not be at the correct point. Sometimes prefocusing in the manual mode allows the camera to set exposure more quickly. EXIF data would tell me the details I really need to help you more.
Have you considered opening a free flickr account (
www.flickr.com) so that you can post larger images?