Yes, he was.
If you can get hold of a copy of the BBC's "Lee, Bell, Summerbee" video, watch it about five times, so that you can really appreciate what he could do.
Nijinsky really had it all and could have played very well in practically any position.
At one point in the video, either Buzzer or Frannie says, "We used to come off the pitch at the end of the game, and we would be bathed in sweat, but Colin was hardly perspiring."
At another point, one of them says that we never really saw Colin at his best. He was still getting better when he was injured.