What am about to explain is no secret, however, for some reason it is seldom discussed when the subject of freezing motion in photography arises. Of course, using the fastest possible shutter peed will solve many "action stopping" problems. What also factors in is the angle at which the subjects are moving toward the camera- straight on, at an angle such as 45 degrees or parallel to the sensor or film plane- this is referred to as the DIRECTION OF THE SUBJECT MOVEMENT. The DISTANCE from the camera to the subject, the FOCAL LENGTH of the lens and the DEGREE OF ENLARGEMENT all have significant influence on motion stopping methodologies.
I am posting a excerpt form an old Kodak Professional Photoguide- which also appeared in my old military field instruction kit. There is a handy chart and a pretty concise explanation of the theory as well a some mathematical formulas to accommodate specific focal lengths and enlargement factors. Be sure to read the part about wide angle and telephoto usage.
Of course, you are not expected to stand there with a calculator or chart in hand when you are trying to shoot a sports event- this theory just gives you some insight into the concept.
In shooting sports events you may require both expanded depth of filed AND fast shutter speeds but sometimes if you need to compromise shutter speed, it's good to know the minimum speed you can use for certain conditions.
Nowadays, with a good DSLR you can really run up the ISO index without too much noise (grain) and shoot at a fast shutter speed AND still be able to enable more depth of field with smaller apertures.
If you read into the guide, it also mentions PANNING WITH THE ACTION.
Another option- If flash is permissible, and the primary exposure is based on the flash, the sensor only "sees" the flash and most current speedlights boast a duration of 1/1000 sec or faster.
In amateur sport situations I often go in and shoot a practice session where I can work, up close with flash and get some nice tight action shots.
The guide is old and based on film photography, however, I find most of it works consistently well in digital work.
I hope this helps and good luck- I'm sure your results will improve one you grasp the program