Photography help eos indoor sports photography?

I was in a sports centre taking photos of a derby game but the images seemed blurred and very dark, I'm new to photography and I'm taking a course but not till the new year, I use a canon eos 1000D with a sigma 70-300mm F4-5.6 DG Macro lens. I had the camera set to the settings stated in camera manual to shoot moving objects etc but I was thinking maybe it's the flash not being strong enough.. Photos I took of people near me' came out fine. Shoul I get a better flash? Or is that not the only problem? Like I said It's all new to me so any advice wud be appreciated