Indoor Field Hockey with Speedlight

With the weather finally improving, I've been looking forward to getting outside for some shots, but this past weekend found me indoors again at a field hockey tournament/fundraiser. I feel that I am getting the hang of shooting with the speedlight (580exII) as the main light, but I am still getting some slight motion blur, as seen on the ball here-

This was shot with a Canon 40D, 135mm f2.0. Shutter was 1/250 (max sync), lens was wide open, iso 200.

I suppose to eliminate that blur I need to reduce the ambient light- I experimented during the day with stopping down the lens or dropping the iso- the problem I ran into was the flash, at ETTL+2 (basically full power), then didn't have the reach to light the players at any reasonable distance. Am I on the right track? It seems like maybe I need more power to the flash in this case, but is there any way to do that with a speedlight? I could set up 2 off-camera, but that limits me to one part of one field- not a good set-up in a situation like this- Multiple fields, 13 teams, rush rush to get them all in.

Thoughts?