To add Kizaru has been super distracted while trying to achieve orders. Its best to wait and see how he'd fight Luffy fully focused.
This is the break in their fight to keep the arc going. Luffy always gets depowered before coming back into the fray when needed. Currently we dont know if Kizaru is even "hurt" or down yet. My guess is this scene with Sentoumaru is supposed to show his defense is something else:
Worst case, he's bloody, serious and lost his glasses I would assume.