Do post an example (or two) and make sure the exposure settings are included. It'll go a long way toward explaining exactly what happened to your shots and why they turned out the way they did.
Many sports are played in environments where the lighting puts the camera at the edge of it's capabilities, if not just a little beyond, when using the kit lens.
Sports mode will bias toward a faster shutter speed and open the aperture. But once the f-stop hits the limit for the lens you are using (e.g. on a kit lens that's usually f/5.6) then it can only continue to increase shutter speed by increasing ISO. If you set the ISO speed to any value other than "Auto" then it's not permitted to alter the ISO -- so it'll be at it's limit. If you did set the ISO to "Auto" then it still has a max based on a setting in the custom functions (e.g. it might have the auto ISO "max" setting at 1600 -- which means that even though the camera can go to 3200, it wont because it was told never to exceed 1600 (or whatever max you've got set) when in "Auto" ISO mode.)
This is a challenge when using the "scene" based modes (portrait, landscape, sports, etc.) is that you're telling the computer the nature of the shot, but you're never really sure what it's doing.
If you learn the fundamentals of exposure, then you could switch to, say, Tv mode (Time value -- aka "Shutter" speed priority.) In that mode you could actually dial in your speed (something in the neighborhood of 1/250th to 1/500th will generally freeze most sports action.) Then as you're taking the shot, you can see the meter in the camera indicating whether it's able to get the shot at the shutter speed you've set. If it's not indicating a good exposure, you'll know it before you take the shots.
A lens with a lower focal ratio will really help your sports shots in situations where the lighting isn't very ideal. A zoom lens with a constant focal ratio of f/2.8 available all throughout the zoom range will collect four times as much light as a variable focal ratio zoom at f/5.6. That means you can shoot with a shutter speed four times faster and get the same shot. You can get non-zoom (aka "prime") lenses that are even faster (e.g. f/2 or lower) and these are collecting eight times or more light. That makes a HUGE difference when shooting sports.