How to Take Outdoor Sports Photographs
Why do people pay all that money for high powered telephoto lenses? They use them to make money. Or at least some of us use that justification when we purchase it! All those great sports photographs are taken with these expensive telephoto lenses. Canon dominates the sports photography field. Somebody has to take sports photographs for the magazines and newspapers!
Image stabilizers can help stabilize the lens with slower shutter speeds, but if there is room at the event Wimberley tripod heads are very useful. The Wimberley tripod head allows you to balance the telephoto lens so you can quickly swing it into position and it will hold that position without camera shake.
Some events are crowded and there is only room for a monopod. Consider getting a Canon 70-200mm f/2.8L IS USM lens first and then assess your situation and what your needs will be. If you are going to make money with it then it is easier to justify the expensive ($3,000-$6,000) lenses.