Since I was mentioned earlier in the thread, thought I'd sign up and put in my $0.02.
The original shot looks like it was shot at ISO 12800, not ISO 500. This is due to increasing the exposure so much in post. As Lori may have mentioned, I shoot a 50D as well and here is one of my shots from last night, in the rain.
Generally, shoot at the ISO you need for the proper exposure. Lower ISO is better, unless you have to brighten it in post, which brings me to... Expose correctly as increasing exposure in post increases noise. Use noise reduction if necessary. It's better to have a grainy shot, than a blurry mess.
50D @ ISO 12800, f/2.8, 1/640
Steve Wampler
Mid TN Sports Photos