I have a tele-reflector that I use with my Norman portables on camera sometimes for bird photos. They're pretty powerful. Should be plenty for sports.

The effect is pretty straight-on, but it does get the light in there, when there might otherwise be no other options--

Alternately, there are fresnel attachments like the Better Beamer and such that can be used with dedicated flash units, so they work with TTL flash metering.