I have used the Tamron, Sigma and the Canon in the 70-200 f2.8. The Tamron while sharper at the 200 length, is very slow to focus and isnt always spot on. A lot of set up is needed to get it right. If you cant go with the Canon, the Sigma is a great choice. It focuses fast and is very good in color reproduction. I personally just got the Canon non IS version and love it. I had rented it numerous times over and probably paid for it twice in rental fees over the last 5 years. It was time I dropped the cash. If you are considering spending a grand, chip in the few extra hundred for the Canon. Otherwise the Sigma will do you great and it doesnt have the stigma of a white lens that some facilities consider a "pro" lens and wont let you in with.
Primes are really nice as well, the downside being with sports and action you have less options. They are a sharper image but you will find yourself limited. They arent always the fastest in the zoom department. I have a 50 1.4 and it focuses super slow at wide open. Gets better in the 2.0-2.8 dept. If you go to the 85 1.8 you will end up stopping it down to 2.8 for the sharper image which is still great indoors, especially under overhead sports lighting. Now high school gyms might find a little bit of issue. You will find yourself wanting to bump the ISO.