It's actually quite interesting if you think about Byakuya's Shikai/Bankai: They are both very slow, and thus would allow almost any opponent jolly good time to counter-attack. I wonder if it's just for that purpose that the guy has invested so much energy to otherwise become so fast. He could evade the enemy attack while preparing his Shikai or Bankai. Or in case the opponent is weak (relatively) like Renji, he just used some demon magic for the same effect. Maybe the opening already showed us Ichigo using this weakness.