After a bit more thought, I'm now almost certain that Luffy, Zoro & Kidd are getting captured coz I can't think of any other reason why Oda woulda knocked Luffy out. Characters have taken worse attacks and not lost consciousness so when Oda does it, you know plot is in play..lolz. Plus Oda's already had Zoro comment on just how formidable it is to take on that many beast pirates who are pretty strong to boot so he's prolly not gonna be able to escape them.